models: Rename Subscription.in_home_view field to is_muted.

This renames Subscription.in_home_view field to is_muted, for greater
clarity as to what it does just from seeing the setting name, without
having to look it up.

Also disabled an obsolete test_migrations test.

Fixes #10042.

zerver/lib/fix_unreads.py

@@ -166,7 +166,7 @@ def fix_pre_pointer(cursor: CursorObj, user_profile: UserProfile) -> None:
             WHERE (
                 zerver_subscription.user_profile_id = '%s' AND
                 zerver_recipient.type = 2 AND
-                zerver_subscription.in_home_view AND
+                (NOT zerver_subscription.is_muted) AND
                 zerver_subscription.active
             )
         '''