ICU-22450 Disable the type_info workaround on newer versions of libstdc++

[glandium]

The workaround for http://llvm.org/bugs/show_bug.cgi?id=13364 is related to an ancient version of libstdc++ (4.6). On the flip side, with more recent versions of GCC, the workaround can cause problems under some conditions.

The _GLIBCXX_RELEASE macro was introduced in libstdc++ 7, checking for it not being defined to enable the workaround makes it disabled with libstdc++ >= 7, which don't need the workaround in the first place.

Checklist

• [x] Required: Issue filed: https://unicode-org.atlassian.net/browse/ICU-22450
• [x] Required: The PR title must be prefixed with a JIRA Issue number.
• [x] Required: The PR description must include the link to the Jira Issue, for example by completing the URL in the first checklist item
• [X] Required: Each commit message must be prefixed with a JIRA Issue number.
• [ ] Issue accepted (done by Technical Committee after discussion)
• [ ] Tests included, if applicable
• [ ] API docs and/or User Guide docs changed or added, if applicable