core[patch]: Fix type for inner input in base prompts (#25713)

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- [ ] **PR title**: "langchain-core: Fix type"
- The file to modify is located in
/libs/core/langchain_core/prompts/base.py


- [ ] **PR message**: 
- **Description:** The change is a type for the inner input variable,
the type go from dict to Any. This change is required since the method
_validate input expects a type that is not only a dictionary.
    - **Dependencies:** There are no dependencies for this change


- [ ] **Add tests and docs**: 
1. A test is not needed. This error occurs because I overrode a portion
of the _validate_input method, which is causing a 'beartype' to raise an
error.

libs/core/langchain_core/prompts/base.py

@@ -129,7 +129,7 @@ def get_input_schema(
             "PromptInput", **{**required_input_variables, **optional_input_variables}
         )
 
-    def _validate_input(self, inner_input: Dict) -> Dict:
+    def _validate_input(self, inner_input: Any) -> Dict:
         if not isinstance(inner_input, dict):
             if len(self.input_variables) == 1:
                 var_name = self.input_variables[0]