Revert "[lldb] Add support for DW_AT_default_value in template params"

This reverts commit 1cf52e540242f968e0cf789587bcf76c01332aeb.

Due to test failures on Arm and AArch64 bots:
https://lab.llvm.org/buildbot/#/builders/96/builds/34718

(which were obscured by an earlier build failure)