Fix T51947: failure setting sequence.use_proxy/crop/translation to False

Referenced by issue #51947, VSE BoolProperties toggle when assigned False

source/blender/blenkernel/intern/sequencer.c

@@ -2082,7 +2082,7 @@ void BKE_sequencer_proxy_set(struct Sequence *seq, bool value)
 		}
 	}
 	else {
-		seq->flag ^= SEQ_USE_PROXY;
+		seq->flag &= ~SEQ_USE_PROXY;
 	}	
 }
 

source/blender/makesrna/intern/rna_sequencer.c

@@ -341,7 +341,7 @@ static void rna_Sequence_use_translation_set(PointerRNA *ptr, int value)
 		}
 	}
 	else {
-		seq->flag ^= SEQ_USE_TRANSFORM;
+		seq->flag &= ~SEQ_USE_TRANSFORM;
 	}
 }
 
@@ -355,7 +355,7 @@ static void rna_Sequence_use_crop_set(PointerRNA *ptr, int value)
 		}
 	}
 	else {
-		seq->flag ^= SEQ_USE_CROP;
+		seq->flag &= ~SEQ_USE_CROP;
 	}
 }