git: Fix tests to not consider dots in identities as crud anymore

When reading both user.name and user.email, Git considers a certain set of characters as crud that will be stripped both from the head and tail of the respective values. This behaviour has changed in 1c04cb0744 (ident: don't consider '.' a crud, 2023-08-02) such that dots are not considered crud anymore. The motivation is e.g. to allow for names such as "John Doe, Jr." to be accepted without modification.

Some of our tests assert that we do indeed strip identities as expected though, including the dot. As the above commit has been merged into the next branch our nightly CI jobs are thus failing.

Adapt our tests to not consider dots as crud anymore.