[FrameworkBundle] Allow to use the BrowserKit assertions with Panther a…

[fabpot]

Q	A
Feature PR	symfony/symfony#32207
PR author(s)	@dunglas
Merged in	pull/32207

[javiereguiluz]

Closing because we don't make any distinction in the docs about this. We only say the come from WebTestCase class.

[dunglas]

@javiereguiluz actually we'll have to remove the mention that it doesn't work with Panther when symfony/panther#205 will be merged