Fix doc string for column 'C&C'

pandas/core/frame.py

@@ -4737,7 +4737,8 @@ def eval(self, expr: str, *, inplace: bool = False, **kwargs) -> Any | None:
         3  4   4    7   8  0
         4  5   2    6   7  3
 
-        For columns with spaces in their name, you can use backtick quoting.
+        For columns with spaces or other disallowed characters in their name, you can
+        use backtick quoting.
 
         >>> df.eval("B * `C&C`")
         0    100