Closes #15228: remove reference to Unix "touch"; it is confusing since the path needs to exist for os.utime() to succeed

Patch by Filip Gruszczyński.

Fix order of required StreamReader/StreamWriter base classes.  Spotted by Edward Welbourne on docs@.

Found by Helge Stenström on docs@.

Fix markup to not add parens to the "hashlib.md5" constructor when the object is meant, not the call.