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_ast.py b/Lib/test/test_ast.py
index 5c37a5f..f35d9e6 100644
--- a/Lib/test/test_ast.py
+++ b/Lib/test/test_ast.py
@@ -551,7 +551,7 @@
             compile(m, "<test>", "exec")
         self.assertIn("but got <_ast.expr", str(cm.exception))
 
-    def test_invalid_identitifer(self):
+    def test_invalid_identifier(self):
         m = ast.Module([ast.Expr(ast.Name(42, ast.Load()))], [])
         ast.fix_missing_locations(m)
         with self.assertRaises(TypeError) as cm: