all: fix typos in comments

Fix its/it's, who's/whose, wether/whether, missing apostrophes
in contractions, and other misspellings across the codebase.

Updates #cleanup

Change-Id: I20453b81a7aceaa14ea2a551abba08a2e7f0a1d8
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

drive/driveimpl/remote_impl.go

@@ -415,7 +415,7 @@ var writeMethods = map[string]bool{
 	"DELETE":    true,
 }
 
-// canSudo checks wether we can sudo -u the configured executable as the
+// canSudo checks whether we can sudo -u the configured executable as the
 // configured user by attempting to call the executable with the '-h' flag to
 // print help.
 func (s *userServer) canSudo() bool {