costattribution.ActiveSeriesTracker: remove duplicate code (#12821)

#### What this PR does

This piece of code duplicates the previous lines, and is never executed
because the previous branches have their return statement.

No changelog or anything needed, this is a noop.

Signed-off-by: Oleg Zaytsev <[email protected]>

Author: colega

pkg/costattribution/active_tracker.go

@@ -110,27 +110,6 @@ func (at *ActiveSeriesTracker) Increment(lbls labels.Labels, now time.Time, nati
 		return
 	}
 
-	if !at.overflowSince.IsZero() {
-		at.observedMtx.RUnlock()
-		at.overflowCounter.activeSeries.Inc()
-		if nativeHistogramBucketNum >= 0 {
-			at.overflowCounter.nativeHistograms.Inc()
-			at.overflowCounter.nativeHistogramBuckets.Add(int64(nativeHistogramBucketNum))
-		}
-		return
-	}
-
-	c, ok = at.observed[string(buf.Bytes())]
-	if ok {
-		c.activeSeries.Inc()
-		if nativeHistogramBucketNum >= 0 {
-			c.nativeHistograms.Inc()
-			c.nativeHistogramBuckets.Add(int64(nativeHistogramBucketNum))
-		}
-		at.observedMtx.RUnlock()
-		return
-	}
-
 	if !at.overflowSince.IsZero() {
 		at.observedMtx.RUnlock()
 		at.overflowCounter.activeSeries.Inc()