tests: remove special handling for undefined memoryview

'memoryview' was introduced in Python 2.7. 4adc090fa2fb added code
to filterpyflakes.py to ignore "undefined name 'memoryview'" pyflakes
warnings. Since we no longer support <Python 2.7, we can remove this
workaround.

tests/filterpyflakes.py

@@ -11,7 +11,7 b' lines = []'
 for line in sys.stdin:
     # We blacklist tests that are too noisy for us
     pats = [
-        r"undefined name '(WindowsError|memoryview)'",
+        r"undefined name 'WindowsError'",
         r"redefinition of unused '[^']+' from line",
     ]
 
@@ -33,7 +33,6 b' for line in lines:'
     sys.stdout.write(line)
 print()
 
-# self test of "undefined name" detection for other than 'memoryview'
+# self test of "undefined name" detection
 if False:
-    print(memoryview)
     print(undefinedname)

tests/test-check-pyflakes.t

@@ -10,5 +10,5 b' run pyflakes on all tracked files ending'
   > -X mercurial/pycompat.py -X contrib/python-zstandard \
   > 2>/dev/null \
   > | xargs pyflakes 2>/dev/null | "$TESTDIR/filterpyflakes.py"
-  tests/filterpyflakes.py:39: undefined name 'undefinedname'
+  tests/filterpyflakes.py:38: undefined name 'undefinedname'