Bump Touch.Unit (dark mode support) (#7020)

New commits in spouliot/Touch.Unit:

* spouliot/Touch.Unit@d22825a [TouchRunner] Fix colors for iOS 13 dark mode (#53)
* spouliot/Touch.Unit@de42aa3 Fallback to "modern" mtouch root if `MONOTOUCH_ROOT` is not set. (#52)
* spouliot/Touch.Unit@a2e1810 Improve logging for failed TCP connections due to hostname (#51)

Diff: 1c41c75983..d22825a7d1

external/Touch.Unit

@@ -1 +1 @@
-Subproject commit 1c41c75983ed840e9dc7079b5d4b0c31d1565359
+Subproject commit d22825a7d13b3a1e96983d132c9d3cfc5ba9762f