Bump pyfxa from 0.7.6 to 0.7.7

Bumps [pyfxa](https://github.com/mozilla/PyFxA) from 0.7.6 to 0.7.7.
- [Release notes](https://github.com/mozilla/PyFxA/releases)
- [Changelog](https://github.com/mozilla/PyFxA/blob/main/CHANGES.txt)
- [Commits](mozilla/PyFxA@v0.7.6...v0.7.7)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

requirements.txt

@@ -25,7 +25,7 @@ plaster==1.0
 plaster-pastedeploy==0.7
 PyBrowserID==0.14.0
 pycparser==2.20
-PyFxA==0.7.6
+PyFxA==0.7.7
 pyramid==1.10.4
 pyramid-multiauth==0.9.0
 pyramid-tm==2.4