Fix SoundCloud false-positive: switch to message-based check (#2355)

* Initial plan

* Fix SoundCloud false-positive: switch from status_code to message checkType

SoundCloud returns HTTP 200 for non-existent user profiles (soft 404),
causing status_code check to report CLAIMED for random usernames.

Switch to message checkType with:
- presenseStrs: hydratable user marker in server-rendered HTML
- absenceStrs: generic page title for non-existent users

Markers sourced from WhatsMyName project's verified SoundCloud entry.

Co-authored-by: soxoj <31013580+soxoj@users.noreply.github.com>
Agent-Logs-Url: https://github.com/soxoj/maigret/sessions/8aa10eef-78bf-4251-bf42-473cd94c7ef4

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: soxoj <31013580+soxoj@users.noreply.github.com>

maigret/resources/data.json

@@ -15230,7 +15230,13 @@
             "tags": [
                 "music"
             ],
-            "checkType": "status_code",
+            "checkType": "message",
+            "presenseStrs": [
+                "\"hydratable\":\"user\""
+            ],
+            "absenceStrs": [
+                "SoundCloud - Hear the world\u2019s sounds"
+            ],
             "urlMain": "https://soundcloud.com/",
             "url": "https://soundcloud.com/{username}",
             "usernameClaimed": "blue",