multiple: Remove unnecessary Ruff suppression comments (#21050)

## Summary

I ran `ruff check --extend-select RUF100 -n` to identify `# noqa`
comments that weren't having any effect in Ruff, and then `ruff check
--extend-select RUF100 -n --fix` on select files to remove all of the
unnecessary `# noqa: F401` violations. It's possible that these were
needed at some point in the past, but they're not necessary in Ruff
v0.1.15 (used by LangChain) or in the latest release.

Co-authored-by: Erick Friis <erick@langchain.dev>

libs/langchain/langchain/chains/llm_math/base.py

@@ -81,7 +81,7 @@ class LLMMathChain(Chain):
         return [self.output_key]
 
     def _evaluate_expression(self, expression: str) -> str:
-        import numexpr  # noqa: F401
+        import numexpr
 
         try:
             local_dict = {"pi": math.pi, "e": math.e}

libs/langchain/langchain/evaluation/parsing/json_distance.py

@@ -46,7 +46,7 @@ class JsonEditDistanceEvaluator(StringEvaluator):
             self._string_distance = string_distance
         else:
             try:
-                from rapidfuzz import distance as rfd  # noqa: F401
+                from rapidfuzz import distance as rfd
             except ImportError:
                 raise ImportError(
                     "The default string_distance operator for the "

libs/langchain/langchain/evaluation/parsing/json_schema.py

@@ -74,7 +74,7 @@ class JsonSchemaEvaluator(StringEvaluator):
         return node
 
     def _validate(self, prediction: Any, schema: Any) -> dict:
-        from jsonschema import ValidationError, validate  # noqa: F401
+        from jsonschema import ValidationError, validate
 
         try:
             validate(instance=prediction, schema=schema)