IR: Remove unnecessary specialization of getSymTab(), NFC

The only specializations of `getSymTab()` were identical to the default
defined in `SymbolTableListTraits::getSymTab()`.  Remove the
specializations, and stop treating it like a configuration point.  Just
to be sure no one else accesses this, make it private.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249469 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed