repetition_quantifier_expects_a_valid_decimal test fails on Fedora

[ignatenkobrain]

---- error_messages::repetition_quantifier_expects_a_valid_decimal stdout ----
thread 'error_messages::repetition_quantifier_expects_a_valid_decimal' panicked at 'assertion failed: `(left == right)`
  left: `"regex parse error:\n    \\\\u{[^}]*}\n        ^\nerror: decimal literal empty"`,
 right: `"regex parse error:\n    \\\\u{[^}]*}\n        ^\nerror: repetition quantifier expects a valid decimal"`', tests/error_messages.rs:16:43

This did not happen on a previous release…

[BurntSushi]

All set. There was a change to how error messages were reported in regex-syntax, which included an integration-style test in regex proper. But I never released the changes to regex-syntax. regex tests still passed since it was using what was on master, but they didn't pass with what was on crates.io. I decided to just move the integration-style test back down into regex-syntax, and cut new releases for both regex and regex-syntax.

This would have been caught by CI if I still had Cargo's minimal version check enabled, but one of the dependencies I rely on considers the minimal version check to be dubious, so I can't use it.