[lldb] drop .symtab removal in minidebuginfo tests

Summary:
After D69041, we no longer have to manually remove the .symtab section
once yaml2obj was run.

Reviewers: espindola, alexshap

Subscribers: emaste, arichardson, MaskRay, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D69254

llvm-svn: 375415