fix: do not check Beta class, since it is Bool in Swift

Easydict/Feature/Configuration/EZConfiguration.m

@@ -665,7 +665,7 @@ - (void)setBeta:(BOOL)beta {
     [NSUserDefaults mm_write:stringValue forKey:EZBetaFeatureKey];
 }
 - (BOOL)isBeta {
-    NSString *stringValue = [NSUserDefaults mm_readString:EZBetaFeatureKey defaultValue:@"0"];
+    NSString *stringValue = [NSUserDefaults mm_read:EZBetaFeatureKey];
     BOOL isBeta = [stringValue boolValue];
     return isBeta;
 }