Revert "Enable usrsctp runtime checks."

This reverts commit 7c0169de.

Reason for revert: Temporary revert to let https://chromium-review.googlesource.com/c/chromium/src/+/2612384 land before the -Wsometimes-uninitialized is addressed upstream.

Original change's description:
> Enable usrsctp runtime checks.
>
> The usrsctp library has a mechanism to enforce invariants (similar to
> CHECK or RTC_CHECK). In order to enable these checks, the macro
> INVARIANTS needs to be defined on all the usrsctp translation units.
>
> Maybe, this macro should be renamed into USRSCTP_ENABLE_CHECKS or at
> least into something with USRSCTP_ as prefix.
>
> This CL enables these runtime checks in debug builds and when the
> build is explicitly asking for them (dcheck_always_on=true).
>
> Bug: None
> Change-Id: Id63d78200ae2a762b86a4dc0c70d1a04e7d94350
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2600903
> Reviewed-by: Harald Alvestrand <hta@chromium.org>
> Commit-Queue: Mirko Bonadei <mbonadei@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#840138}

TBR=hta@chromium.org,deadbeef@chromium.org,mbonadei@chromium.org,orphis@chromium.org,chromium-scoped@luci-project-accounts.iam.gserviceaccount.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: None
Change-Id: Ifd63fad568cfdad45fe5330948e1fb616ba1c5cd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2614406Reviewed-by: Mirko Bonadei <mbonadei@chromium.org>
Reviewed-by: Harald Alvestrand <hta@chromium.org>
Commit-Queue: Mirko Bonadei <mbonadei@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841006}

third_party/usrsctp/BUILD.gn

@@ -2,7 +2,6 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import("//build/config/dcheck_always_on.gni")
 import("//build/toolchain/toolchain.gni")
 
 config("usrsctp_config") {
@@ -11,18 +10,10 @@ config("usrsctp_config") {
     "usrsctplib/usrsctplib/netinet",
   ]
 
-  defines = []
-
-  if (is_debug || dcheck_always_on) {
-    defines += [
-      "INVARIANTS",  # Enable runtime checks.
-    ]
-  }
-
   # This is part of the public config because it's used both by usrsctp and
   # the client (WebRTC), to determine if the length field needs populating.
   if (is_mac || is_ios || target_os == "freebsd") {
-    defines += [ "HAVE_SCONN_LEN" ]
+    defines = [ "HAVE_SCONN_LEN" ]
   }
 }