Do not throw exception when casting to int.

Make String#number? patch more efficient by not having an alternate path in case cast was not possible.

The inefficiency was identified in Rack::Timeout::RequestTimeoutException on parti... (gitlab-org/gitlab#435272 - closed). Profiling the reported request showed that the Integer cast in this gem was taking up a significant amount of wall time. Further investigation showed that the failure was happening occurring only for cases when the string was not a proper number.

I benchmarked and tested 2 alternatives (regex and casting without an exception) here: gitlab-org/gitlab#435272 (comment 1735216350)

Note: I went with a MINOR update rather than a PATCH as this is not a fix per se and may affect some functionality.