Reenable test_gdb
    
    Python 3.8.3 skips test_gdb tests when it detects that gdb fails to
    read debug information like "frame information optimized out":
    
    https://bugs.python.org/issue40019
    https://github.com/python/cpython/commit/4ced9a7611ddfd923bd8f72aa61121d0e5aeb8fc
    
    Resolves: rhbz#1818857