De-deprecate MatchingOptions.matchLevel (#390)

Removing this deprecation warning, as it's just generating noise.
We may still eventually want to remove _CharacterClassModel.matchLevel
along with other refactoring in the future.

Author: natecook1000

Sources/_StringProcessing/MatchingOptions.swift

@@ -117,7 +117,6 @@ extension MatchingOptions {
 
 // Deprecated CharacterClass.MatchLevel API
 extension MatchingOptions {
-  @available(*, deprecated)
   var matchLevel: _CharacterClassModel.MatchLevel {
     switch semanticLevel {
     case .graphemeCluster: