refactor(content_management): remove unused search change events

- Remove CreateSourceCountrySearchChanged and CreateSourceLanguageSearchChanged events
- These events were not used in the bloc logic and have been removed to simplify the codebase

Author: fulleni

lib/content_management/bloc/create_source/create_source_event.dart

@@ -76,27 +76,11 @@ final class CreateSourceSubmitted extends CreateSourceEvent {
   const CreateSourceSubmitted();
 }
 
-/// Event for when the country search term is changed.
-final class CreateSourceCountrySearchChanged extends CreateSourceEvent {
-  const CreateSourceCountrySearchChanged(this.searchTerm);
-  final String searchTerm;
-  @override
-  List<Object?> get props => [searchTerm];
-}
-
 /// Event to request loading more countries.
 final class CreateSourceLoadMoreCountriesRequested extends CreateSourceEvent {
   const CreateSourceLoadMoreCountriesRequested();
 }
 
-/// Event for when the language search term is changed.
-final class CreateSourceLanguageSearchChanged extends CreateSourceEvent {
-  const CreateSourceLanguageSearchChanged(this.searchTerm);
-  final String searchTerm;
-  @override
-  List<Object?> get props => [searchTerm];
-}
-
 /// Event to request loading more languages.
 final class CreateSourceLoadMoreLanguagesRequested extends CreateSourceEvent {
   const CreateSourceLoadMoreLanguagesRequested();