Delete 'num_temporal_layers > 4' dead code path.

At some point this code path was used for the
WebRTC-VP8ConferenceTemporalLayers experiment, but that has been
deleted.

The API does not allow creating more than 3 temporal layers so this
should be dead code and deleting it causes no test failures.

Bug: None
Change-Id: Ie13bc09a7af996d081ab5702d1bb8d17c6021ce4
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/377300
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Erik Språng <sprang@webrtc.org>
Auto-Submit: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#43900}
diff --git a/video/config/simulcast.cc b/video/config/simulcast.cc
index 0893b4c..35be2f7 100644
--- a/video/config/simulcast.cc
+++ b/video/config/simulcast.cc
@@ -320,12 +320,6 @@
           // Base heavy allocation increases TL0 bitrate from 40% to 60%.
           rate_factor = 0.4 / 0.6;
         }
-      } else if (num_temporal_layers > 3) {
-        rate_factor =
-            webrtc::SimulcastRateAllocator::GetTemporalRateAllocation(
-                3, 0, /*base_heavy_tl3_rate_alloc=*/false) /
-            webrtc::SimulcastRateAllocator::GetTemporalRateAllocation(
-                num_temporal_layers, 0, /*base_heavy_tl3_rate_alloc=*/false);
       }
 
       layers[s].max_bitrate_bps =