Auto merge of #18040 - atouchet:user-agent, r=jdm
Auto merge of #18040 - atouchet:user-agent, r=jdm

Update Firefox version in user agent

<!-- Please describe your changes on the following line: -->
GitHub has started throwing warnings about using an outdated version of Firefox when loaded with Servo. I am assuming that this is due to Servo using Firefox 37.0 in its user agent which was set in 2015 and hasn't been updated since then. I don't know if updating this should cause any site compatibility issues or not.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

<!-- Either: -->
- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/18040)
<!-- Reviewable:end -->

avadacatavra/servo,saneyuki/servo,dsandeephegde/servo,CJ8664/servo,larsbergstrom/servo,upsuper/servo,CJ8664/servo,larsbergstrom/servo,cbrewster/servo,szeged/servo,szeged/servo,canaltinova/servo,fiji-flo/servo,eddyb/servo,avadacatavra/servo,splav/servo,splav/servo,splav/servo,emilio/servo,dsandeephegde/servo,larsbergstrom/servo,KiChjang/servo,mbrubeck/servo,paulrouget/servo,peterjoel/servo,notriddle/servo,saneyuki/servo,cbrewster/servo,sadmansk/servo,anthgur/servo,jimberlage/servo,sadmansk/servo,mbrubeck/servo,thiagopnts/servo,szeged/servo,mbrubeck/servo,ConnorGBrewster/servo,nnethercote/servo,sadmansk/servo,emilio/servo,paulrouget/servo,nnethercote/servo,pyfisch/servo,canaltinova/servo,mbrubeck/servo,mbrubeck/servo,peterjoel/servo,eddyb/servo,thiagopnts/servo,splav/servo,nnethercote/servo,splav/servo,pyfisch/servo,CJ8664/servo,paulrouget/servo,nnethercote/servo,paulrouget/servo,dati91/servo,KiChjang/servo,ConnorGBrewster/servo,sadmansk/servo,saneyuki/servo,upsuper/servo,KiChjang/servo,larsbergstrom/servo,mattnenterprise/servo,KiChjang/servo,larsbergstrom/servo,pyfisch/servo,larsbergstrom/servo,CJ8664/servo,saneyuki/servo,splav/servo,notriddle/servo,mattnenterprise/servo,dati91/servo,sadmansk/servo,nnethercote/servo,splav/servo,dsandeephegde/servo,DominoTree/servo,jimberlage/servo,emilio/servo,notriddle/servo,saneyuki/servo,mattnenterprise/servo,CJ8664/servo,SimonSapin/servo,eddyb/servo,paulrouget/servo,peterjoel/servo,anthgur/servo,cbrewster/servo,mbrubeck/servo,emilio/servo,thiagopnts/servo,mattnenterprise/servo,SimonSapin/servo,splav/servo,thiagopnts/servo,DominoTree/servo,peterjoel/servo,fiji-flo/servo,thiagopnts/servo,dati91/servo,notriddle/servo,larsbergstrom/servo,upsuper/servo,notriddle/servo,cbrewster/servo,avadacatavra/servo,szeged/servo,jimberlage/servo,emilio/servo,DominoTree/servo,canaltinova/servo,ConnorGBrewster/servo,fiji-flo/servo,DominoTree/servo,larsbergstrom/servo,saneyuki/servo,canaltinova/servo,CJ8664/servo,mattnenterprise/servo,dati91/servo,eddyb/servo,anthgur/servo,dsandeephegde/servo,anthgur/servo,notriddle/servo,mattnenterprise/servo,pyfisch/servo,cbrewster/servo,splav/servo,dati91/servo,rnestler/servo,emilio/servo,jimberlage/servo,paulrouget/servo,nnethercote/servo,nnethercote/servo,emilio/servo,canaltinova/servo,rnestler/servo,dsandeephegde/servo,rnestler/servo,pyfisch/servo,CJ8664/servo,paulrouget/servo,szeged/servo,CJ8664/servo,avadacatavra/servo,szeged/servo,rnestler/servo,DominoTree/servo,DominoTree/servo,KiChjang/servo,eddyb/servo,DominoTree/servo,rnestler/servo,DominoTree/servo,dsandeephegde/servo,notriddle/servo,upsuper/servo,anthgur/servo,thiagopnts/servo,avadacatavra/servo,avadacatavra/servo,jimberlage/servo,larsbergstrom/servo,avadacatavra/servo,KiChjang/servo,szeged/servo,KiChjang/servo,sadmansk/servo,dsandeephegde/servo,pyfisch/servo,szeged/servo,canaltinova/servo,sadmansk/servo,avadacatavra/servo,paulrouget/servo,thiagopnts/servo,nnethercote/servo,SimonSapin/servo,fiji-flo/servo,paulrouget/servo,KiChjang/servo,canaltinova/servo,pyfisch/servo,szeged/servo,jimberlage/servo,SimonSapin/servo,cbrewster/servo,nnethercote/servo,ConnorGBrewster/servo,pyfisch/servo,peterjoel/servo,KiChjang/servo,mattnenterprise/servo,emilio/servo,pyfisch/servo,thiagopnts/servo,fiji-flo/servo,upsuper/servo,anthgur/servo,jimberlage/servo,ConnorGBrewster/servo,peterjoel/servo,peterjoel/servo,dati91/servo,eddyb/servo,canaltinova/servo,jimberlage/servo,saneyuki/servo,saneyuki/servo,upsuper/servo,ConnorGBrewster/servo,fiji-flo/servo,mbrubeck/servo,peterjoel/servo,sadmansk/servo,cbrewster/servo,jimberlage/servo,eddyb/servo,rnestler/servo,anthgur/servo,peterjoel/servo,nnethercote/servo,SimonSapin/servo,fiji-flo/servo,splav/servo,SimonSapin/servo,peterjoel/servo,SimonSapin/servo,upsuper/servo,anthgur/servo,notriddle/servo,ConnorGBrewster/servo,cbrewster/servo,pyfisch/servo,mbrubeck/servo,rnestler/servo,szeged/servo,dati91/servo,SimonSapin/servo,dsandeephegde/servo,ConnorGBrewster/servo,larsbergstrom/servo,dati91/servo,saneyuki/servo,DominoTree/servo,rnestler/servo,saneyuki/servo,eddyb/servo,DominoTree/servo,emilio/servo,emilio/servo,KiChjang/servo,upsuper/servo,notriddle/servo,notriddle/servo,fiji-flo/servo,mattnenterprise/servo,paulrouget/servo