Remove gdb-6.5-readline-long-line-crash-test.patch
    
    Remove gdb-6.5-readline-long-line-crash-test.patch, this test is now
    upstream in commit:
    
      commit bb146a79c7d65e2b578e8c3f652cb118c63741e5
      Date:   Thu Feb 9 10:52:47 2023 +0000
    
          gdb: add test for readline handling very long commands
    
    As this is only a test, I don't see any point in backporting the
    upstream commit, we'll pick this up with a later rebase.