chore: Add missing localization

lib/l10n/intl_en.arb

@@ -3497,5 +3497,6 @@
   "signInGreeting": "You already have an account in Matrix? Welcome back! Select your homeserver and sign in.",
   "appIntro": "With FluffyChat you can chat with your friends. It's a secure decentralized [matrix] messenger! Learn more on https://matrix.org if you like or just sign up.",
   "theProcessWasCanceled": "The process was canceled.",
-  "join": "Join"
+  "join": "Join",
+  "searchOrEnterHomeserverAddress": "Search or enter homeserver address"
 }

lib/pages/sign_in/sign_in_page.dart

@@ -69,7 +69,9 @@ class SignInPage extends StatelessWidget {
                         errorText: state.publicHomeservers.error
                             ?.toLocalizedString(context),
                         prefixIcon: const Icon(Icons.search_outlined),
-                        hintText: 'Search or enter homeserver address',
+                        hintText: L10n.of(
+                          context,
+                        ).searchOrEnterHomeserverAddress,
                       ),
                     ),
                   ],