Strip semicolons from supplied repository fingerprint

When adding a repository specifying its fingerprint many users insert it with semicolons (4C:C3:E0:6E:72:67...), and the verification fails. This happens because the semicolon format is used very often, it's the way keytool prints it and F-Droid itself uses it when displaying the details if a repository.

I suggest stripping the semicolons from the user supplied fingerprint. This should be as easy as adding a replace(':', '') in verifyAndStoreTOFUCerts and should not have any side effect.