fix(parse): permit unbraced initializer after requires

[JohelEGP]

Resolves #423.

Testing summary.

100% tests passed, 0 tests failed out of 508

Total Test time (real) = 123.03 sec

Acknowledgements.

• Tested thanks to https://github.com/modern-cmake/cppfront.
• The commit message uses Conventional Commits 1.0.0.

[JohelEGP]

I think the test happens to work, despite #323,
because the definition overloads with the declaration.
So actually not emitting the requires on the declaration
wouldn't be a fix even for GCC 10.
IOW, GCC 10 can't support order independence for a declaration with a requires clause.

[hsutter]

Thanks! Looks good, nice fix.

Re requires and GCC 10: I'm going to move the baseline GCC from 10 up to 11 to rely on the requires bugfix in GCC 11 (and test with 13, which you've already started creating a regression test directory for). Enabling that requires emission on the declaration will be another update...