NetEq: Removing two asserts

These asserts cover error cases that are also handled by the code
after the assert. Should not have both assert and error handling.

BUG=webrtc:4840

Review URL: https://codereview.webrtc.org/1321023002

Cr-Original-Commit-Position: refs/heads/master@{#9804}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 98f3cc54daf0385e8b76875aa4ea0cb16987bfc5
diff --git a/modules/audio_coding/neteq/neteq_impl.cc b/modules/audio_coding/neteq/neteq_impl.cc
index 00f854b..beadeda 100644
--- a/modules/audio_coding/neteq/neteq_impl.cc
+++ b/modules/audio_coding/neteq/neteq_impl.cc
@@ -712,7 +712,6 @@
   int return_value = GetDecision(&operation, &packet_list, &dtmf_event,
                                  &play_dtmf);
   if (return_value != 0) {
-    assert(false);
     last_mode_ = kModeError;
     return return_value;
   }
@@ -980,7 +979,6 @@
     if (*play_dtmf && !header) {
       timestamp_ = dtmf_event->timestamp;
     } else {
-      assert(header);
       if (!header) {
         LOG(LS_ERROR) << "Packet missing where it shouldn't.";
         return -1;