Remove incorrect value description for -enable-polly-aligned

The description of the parameter value passed to -enable-polly-aligned did
not make any sense at all, but was just a leftover coming from when this option
was copied form -enable-polly-openmp. We just drop it as the option description
gives sufficient information already.

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@220445 91177308-0d34-0410-b5e6-96231b3b80d8