code: remove unneeded comparison eval wrapper

Given a `RecursionError` traceback, the `Traceback.recursionindex()`
method returns the index of the frame which started the recursion
(repeated set of frames). To do so it attempts to check whether two
frames are equivalent. Just checking the function/line is not enough
because the recursion variable(s) might differ (e.g. imagine the numeric
value in a recursive factorial implementation). So it also compares the
`f_locals` (local variables) of each frame for equivalence.

For some reason, the locals comparison is wrapped in an `eval` whose
purpose is to evaluate the comparison in one of the compared frame's
context (locals + globals in scope). However, I can not think of any way
in which the global scope could affect the evaluation. It would have an
affect when the locals are bound but that's already done. So this seems
unnecessary - remove it.

Author: bluetech

src/_pytest/_code/code.py

@@ -422,21 +422,12 @@ def recursionindex(self) -> Optional[int]:
                 f = entry.frame
                 loc = f.f_locals
                 for otherloc in values:
-                    if f.eval(
-                        co_equal,
-                        __recursioncache_locals_1=loc,
-                        __recursioncache_locals_2=otherloc,
-                    ):
+                    if otherloc == loc:
                         return i
             values.append(entry.frame.f_locals)
         return None
 
 
-co_equal = compile(
-    "__recursioncache_locals_1 == __recursioncache_locals_2", "?", "eval"
-)
-
-
 E = TypeVar("E", bound=BaseException, covariant=True)