SI-6816 Deprecate -Yeta-expand-keeps-star

This commit deprecates the -Yeta-expand-keeps-star flag. It was created
in 2.10 to help in the transition from 2.9 but by the time 2.11 comes
out it should no longer be necessary.
Merge pull request #2187 from JamesIry/master_SI-6816

SI-6816 Deprecate -Yeta-expand-keeps-star