Refine copy

src/i18n/en/components/timeline.json

@@ -107,7 +107,7 @@
             "accessibilityHint": "User's account"
           }
         },
-        "application": "Tooted with {{application}}",
+        "application": "Via {{application}}",
         "edited": {
           "accessibilityLabel": "Toot edited"
         },

src/i18n/en/screens/tabs.json

@@ -295,7 +295,7 @@
       },
       "followed_by": " is following you",
       "moved": "User moved",
-      "created_at": "Registered on: {{date}}",
+      "created_at": "Joined: {{date}}",
       "summary": {
         "statuses_count": "{{count}} toots",
         "following_count": "$t(shared.users.accounts.following)",