Fix typos in comments, docs and test names (#15018)

* Fix typos in comments, docs and test names

* Update test_pyparse.py

account for change in string length

* Apply suggestion: splitable -> splittable

Co-Authored-By: Terry Jan Reedy <tjreedy@udel.edu>

* Apply suggestion: splitable -> splittable

Co-Authored-By: Terry Jan Reedy <tjreedy@udel.edu>

* Apply suggestion: Dealloccte -> Deallocate

Co-Authored-By: Terry Jan Reedy <tjreedy@udel.edu>

* Update posixmodule checksum.

* Reverse idlelib changes.
diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
index e58d092..4fe74bf 100644
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -1500,7 +1500,7 @@
     def test_run_with_pathlike_path(self):
         # bpo-31961: test run(pathlike_object)
         # the name of a command that can be run without
-        # any argumenets that exit fast
+        # any arguments that exit fast
         prog = 'tree.com' if mswindows else 'ls'
         path = shutil.which(prog)
         if path is None: