Cleaning up unnecessary headers

Signal/src/environment/PropertyListPreferences.h

@@ -12,9 +12,6 @@
 -(id) adjustAndTryGetNewValueForKey:(NSString*)key afterAdjuster:(id (^)(id oldValue))adjuster;
 -(void) clear;
 
--(void) secureTryValueForKey:(NSString *)key toValue:(id)value;
--(NSData*) secureTryGetDataForKey:(NSString *)key;
--(NSString*) secureTryGetStringForKey:(NSString *)key;
 -(NSData*) secureDataStoreAdjustAndTryGetNewValueForKey:(NSString *)key afterAdjuster:(id (^)(id))adjuster;
 -(NSString*) secureStringStoreAdjustAndTryGetNewValueForKey:(NSString *)key afterAdjuster:(id (^)(id))adjuster;