Remove unneded debug constant (#8762)

I added it recently before I discovered `--mypyc-showc`.

mypyc/test/test_run.py

@@ -51,9 +51,6 @@
 
 WORKDIR = 'build'
 
-# This will dump content of all generated C files.
-VERBOSE_DEBUG_DUMP = False
-
 
 def run_setup(script_name: str, script_args: List[str]) -> bool:
     """Run a setup script in a somewhat controlled environment.
@@ -219,12 +216,6 @@ def run_case_step(self, testcase: DataDrivenTestCase, incremental_step: int) ->
                 errors=errors,
                 groups=groups,
             )
-            if VERBOSE_DEBUG_DUMP:
-                for group in cfiles:
-                    for name, content in group:
-                        print(name)
-                        print('-' * len(name))
-                        print(content + '\n')
             if errors.num_errors:
                 errors.flush_errors()
                 assert False, "Compile error"