Revert benchmark related changes

Author: JukkaL

mypyc/build.py

@@ -588,7 +588,6 @@ def mypycify(
     build_dir = compiler_options.target_dir
 
     cflags: list[str] = []
-    opt_level = 3
     if compiler.compiler_type == "unix":
         cflags += [
             f"-O{opt_level}",

mypyc/test-data/run-classes.test

@@ -5467,34 +5467,3 @@ def test_read_corrupted_data() -> None:
             print("RANDOMIZED TEST FAILURE -- please open an issue with the following context:")
             print(">>>", e, data)
             raise
-
-
-
-[case testXXX_librt_internal]
-from librt.internal import WriteBuffer, ReadBuffer, write_int, read_int
-
-import time
-
-
-def bench(data: bytes, n: int) -> None:
-    for i in range(10 * 1000):
-        b = ReadBuffer(data)
-        for i in range(n):
-            read_int(b)
-
-
-w = WriteBuffer()
-N = 400 * 1000
-for i in range(N):
-    write_int(w, i & 63)
-
-d = w.getvalue()
-
-bench(d, N)
-
-def test_foo() -> None:
-    t0 = time.time()
-    bench(d, N)
-    print("===>", time.time() - t0)
-    print()
-    assert False