* Adjust version numbers and a test to conform to the SemVer spec.
Gson releases since 2.8.0 have been following this spec. We mistakenly released 2.10
without the .0 patch version, and adjusted `GsonVersionDiagnosticsTest` so it would
accept that, as well as the two-digit `10`. Here we make the test no longer accept
versions without a patch number, while still accepting two-digit minor versions of course.
We also change the snapshot version to 2.11.0-SNAPSHOT instead of 2.11-SNAPSHOT.
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