minor #30538 [Messenger] Fix README about BC promise (nicolas-grekas)
minor #30538 [Messenger] Fix README about BC promise (nicolas-grekas)

This PR was merged into the 4.2 branch.

Discussion
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[Messenger] Fix README about BC promise

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

We don't have a BC *break* policy :)
Should be applied to MIME and HttpClient when merging into master.

Commits
-------

9b2af69403 Fix README about BC promise

jderusse/symfony,symfony/symfony,Simperfit/symfony,shieldo/symfony,arjenm/symfony,tgalopin/symfony,zorn-v/symfony,yceruto/symfony,vincentaubert/symfony,andreia/symfony,hhamon/symfony,maidmaid/symfony,mweimerskirch/symfony,HeahDude/symfony,ro0NL/symfony,garak/symfony,arjenm/symfony,jakzal/symfony,joelwurtz/symfony,mweimerskirch/symfony,phramz/symfony,sgehrig/symfony,Slamdunk/symfony,smatyas/symfony,localheinz/symfony,xabbuh/symfony,Simperfit/symfony,MatTheCat/symfony,Tobion/symfony,jvasseur/symfony,bendavies/symfony,oleg-andreyev/symfony,arjenm/symfony,pierredup/symfony,docteurklein/symfony,dmaicher/symfony,jakzal/symfony,lyrixx/symfony,Simperfit/symfony,zerkms/symfony,OskarStark/symfony,xabbuh/symfony,ragboyjr/symfony,Deamon/symfony,mnapoli/symfony,joelwurtz/symfony,zorn-v/symfony,mweimerskirch/symfony,tgalopin/symfony,vincentaubert/symfony,Koc/symfony,zcodes/symfony,dmaicher/symfony,derrabus/symfony,Slamdunk/symfony,HeahDude/symfony,maidmaid/symfony,sgehrig/symfony,jakzal/symfony,smatyas/symfony,jvasseur/symfony,pierredup/symfony,phramz/symfony,xabbuh/symfony,jderusse/symfony,vincentaubert/symfony,yceruto/symfony,lstrojny/symfony,damienalexandre/symfony,OskarStark/symfony,teohhanhui/symfony,Tobion/symfony,voronkovich/symfony,stof/symfony,oleg-andreyev/symfony,hhamon/symfony,chalasr/symfony,MatTheCat/symfony,hhamon/symfony,sroze/symfony,chalasr/symfony,OskarStark/symfony,damienalexandre/symfony,Nyholm/symfony,fabpot/symfony,HeahDude/symfony,dmaicher/symfony,ragboyjr/symfony,smatyas/symfony,d-ph/symfony,jakzal/symfony,stof/symfony,docteurklein/symfony,gnat42/symfony,curry684/symfony,OskarStark/symfony,zerkms/symfony,Deamon/symfony,kbond/symfony,yceruto/symfony,ragboyjr/symfony,chalasr/symfony,docteurklein/symfony,Tobion/symfony,nicolas-grekas/symfony,oleg-andreyev/symfony,localheinz/symfony,d-ph/symfony,joelwurtz/symfony,mpdude/symfony,andreia/symfony,lstrojny/symfony,mweimerskirch/symfony,Taluu/symfony,kbond/symfony,zcodes/symfony,symfony/symfony,pyrech/symfony,bendavies/symfony,paradajozsef/symfony,mnapoli/symfony,garak/symfony,symfony/symfony,smatyas/symfony,ogizanagi/symfony,romaricdrigon/symfony,voronkovich/symfony,romaricdrigon/symfony,xabbuh/symfony,ogizanagi/symfony,alekitto/symfony,ogizanagi/symfony,andreia/symfony,Taluu/symfony,nicolas-grekas/symfony,pierredup/symfony,derrabus/symfony,garak/symfony,alekitto/symfony,vincentaubert/symfony,shieldo/symfony,zorn-v/symfony,d-ph/symfony,Deamon/symfony,curry684/symfony,mnapoli/symfony,alekitto/symfony,ragboyjr/symfony,teohhanhui/symfony,mnapoli/symfony,chalasr/symfony,Koc/symfony,garak/symfony,1ed/symfony,zerkms/symfony,d-ph/symfony,tgalopin/symfony,jderusse/symfony,Deamon/symfony,jvasseur/symfony,ro0NL/symfony,damienalexandre/symfony,paradajozsef/symfony,Nyholm/symfony,Slamdunk/symfony,mpdude/symfony,Koc/symfony,pyrech/symfony,smatyas/symfony,Deamon/symfony,maidmaid/symfony,gonzalovilaseca/symfony,kbond/symfony,jvasseur/symfony,andreia/symfony,sgehrig/symfony,docteurklein/symfony,fabpot/symfony,tucksaun/symfony,shieldo/symfony,teohhanhui/symfony,teohhanhui/symfony,Nyholm/symfony,symfony/symfony,Taluu/symfony,stof/symfony,pyrech/symfony,nicolas-grekas/symfony,mpdude/symfony,ajgarlag/symfony,oleg-andreyev/symfony,mnapoli/symfony,romaricdrigon/symfony,fabpot/symfony,gnat42/symfony,romaricdrigon/symfony,bendavies/symfony,zcodes/symfony,arjenm/symfony,gonzalovilaseca/symfony,1ed/symfony,ajgarlag/symfony,sroze/symfony,kbond/symfony,pyrech/symfony,hhamon/symfony,ro0NL/symfony,joelwurtz/symfony,Simperfit/symfony,pierredup/symfony,bendavies/symfony,curry684/symfony,zerkms/symfony,gonzalovilaseca/symfony,docteurklein/symfony,Taluu/symfony,tucksaun/symfony,localheinz/symfony,ro0NL/symfony,nicolas-grekas/symfony,zorn-v/symfony,sroze/symfony,tucksaun/symfony,fabpot/symfony,damienalexandre/symfony,sroze/symfony,MatTheCat/symfony,paradajozsef/symfony,derrabus/symfony,zcodes/symfony,curry684/symfony,MatTheCat/symfony,voronkovich/symfony,Nyholm/symfony,Tobion/symfony,paradajozsef/symfony,voronkovich/symfony,Slamdunk/symfony,1ed/symfony,gonzalovilaseca/symfony,jderusse/symfony,Koc/symfony,Simperfit/symfony,localheinz/symfony,maidmaid/symfony,yceruto/symfony,stof/symfony,lyrixx/symfony,sgehrig/symfony,shieldo/symfony,alekitto/symfony,mpdude/symfony,lyrixx/symfony,lyrixx/symfony,HeahDude/symfony,ajgarlag/symfony,derrabus/symfony,lstrojny/symfony,mweimerskirch/symfony,tucksaun/symfony,phramz/symfony,gnat42/symfony,1ed/symfony,ajgarlag/symfony,dmaicher/symfony,phramz/symfony,tgalopin/symfony,gnat42/symfony,ogizanagi/symfony