av1_scale_acskip_thresh: remove dead store on return

this also changes to code to use one common return path which has the
side-effect of removing an else after a previous return:
https://clang.llvm.org/extra/clang-tidy/checks/readability/else-after-return.html

Change-Id: I5908cbf59f670487df774c2bc941da9c7558f8c4
diff --git a/av1/encoder/av1_temporal_denoiser.c b/av1/encoder/av1_temporal_denoiser.c
index 6194925..8b59c06 100644
--- a/av1/encoder/av1_temporal_denoiser.c
+++ b/av1/encoder/av1_temporal_denoiser.c
@@ -693,10 +693,9 @@
                                 AV1_DENOISER_LEVEL noise_level, int abs_sumdiff,
                                 int temporal_layer_id) {
   if (noise_level >= kDenLow && abs_sumdiff < 5)
-    return threshold *=
-           (noise_level == kDenLow) ? 2 : (temporal_layer_id == 2) ? 10 : 6;
-  else
-    return threshold;
+    threshold *=
+        (noise_level == kDenLow) ? 2 : (temporal_layer_id == 2) ? 10 : 6;
+  return threshold;
 }
 
 void av1_denoiser_reset_on_first_frame(AV1_COMP *const cpi) {