[DebugInfo][NFC] Remove handler with ErrorPolicy from DWARFContext.

Summary:
Current LLVM code base does not use error handler with ErrorPolicy.
This patch removes ErrorPolicy from DWARFContext.

This patch is extracted from the D74308.

Reviewers: jhenderson, dblaikie, grimar, aprantl, JDevlieghere

Reviewed By: grimar

Subscribers: hiraditya, llvm-commits

Tags: #llvm, #debug-info

Differential Revision: https://reviews.llvm.org/D75118