Unit test expected results file names contain invalid characters

This is due to these files having invalid filenames on Windows systems, file names should not contain ":" (colons).

These files cause issues during installation on a Windows based system and colons are replaced with underscores.
In addition Windows <> Linux interoperability is affected, FTP transfers of said files from Linux to Windows fails with the error The directory or file cannot be created.

The manual installation of the plugin might also be affected depending on the archiving software used to extract the "zip" file and it's handling of the characters.

The specific files are as follows:

• tests/expected/LoginFailTest::test_process_login_fail__post_threshold
• tests/expected/LoginFailTest::test_wp_login__post_breach_threshold

Also as per ​WordPress Coding Standards:

Files should be named descriptively using lowercase letters. Hyphens should separate words.