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>

cmd/tailscale/cli/serve_v2.go

@@ -1096,7 +1096,7 @@ func isRemote(target string) bool {
 		target = "tmp://" + target
 	}
 
-	// make sure we can parse the target, wether it's a full URL or just a host:port
+	// make sure we can parse the target, whether it's a full URL or just a host:port
 	u, err := url.ParseRequestURI(target)
 	if err != nil {
 		// If we can't parse the target, it doesn't matter if it's remote or not