[llvm] [utils][filecheck-lint]: speedup filecheck_lint (PR #94191)

[Benjamin Chetioui via llvm-commits]

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@@ -78,32 +78,41 @@ def levenshtein(s1: str, s2: str) -> int:  # pylint: disable=g-doc-args
 
 
 class FileRange:
-    """Stores the coordinates of a span on a single line within a file.
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bchetioui wrote:

We only "derive" in `as_str`, so I think this docstring should still say "Stores".

https://github.com/llvm/llvm-project/pull/94191