[script/textinput] Fix warning: unreachable pattern
[script/textinput] Fix warning: unreachable pattern

The `cfg` attribute in use resulted in two match arms for two cases on
`macos`. Since both arms had a main functionality in common, I merged
them and conditions the extra `macos` part.

```
warning: unreachable pattern
   -->
/Users/behnam/code/servo/servo/components/script/textinput.rs:696:13
    |
696 |             (None, Key::Home) => {
    |             ^^^^^^^^^^^^^^^^^
    |
    = note: #[warn(unreachable_patterns)] on by default

warning: unreachable pattern
   -->
/Users/behnam/code/servo/servo/components/script/textinput.rs:700:13
    |
700 |             (None, Key::End) => {
    |             ^^^^^^^^^^^^^^^^
    |
    = note: #[warn(unreachable_patterns)] on by default
```

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