fix: Properly put OM text p.CreatedTimestamp behind feature flag (#14809)

Mitigates https://github.com/prometheus/prometheus/issues/14808

Signed-off-by: Manik Rana <manikrana54@gmail.com>

scrape/scrape.go

@@ -1634,7 +1634,8 @@ loop:
 		if seriesAlreadyScraped && parsedTimestamp == nil {
 			err = storage.ErrDuplicateSampleForTimestamp
 		} else {
-			if ctMs := p.CreatedTimestamp(); sl.enableCTZeroIngestion && ctMs != nil {
+			if sl.enableCTZeroIngestion {
+				if ctMs := p.CreatedTimestamp(); ctMs != nil {
 					ref, err = app.AppendCTZeroSample(ref, lset, t, *ctMs)
 					if err != nil && !errors.Is(err, storage.ErrOutOfOrderCT) { // OOO is a common case, ignoring completely for now.
 						// CT is an experimental feature. For now, we don't need to fail the
@@ -1642,6 +1643,7 @@ loop:
 						level.Debug(sl.l).Log("msg", "Error when appending CT in scrape loop", "series", string(met), "ct", *ctMs, "t", t, "err", err)
 					}
 				}
+			}
 
 			if isHistogram && sl.enableNativeHistogramIngestion {
 				if h != nil {