Revert "Add winmm.lib as a Windows dep for timeutils."

This reverts commit 9e06ce0afbe0319509b3c4cd2494ae9330662926.

Reason for revert: Speculative fix for failing Win32 Release buildbot

Original change's description:
> Add winmm.lib as a Windows dep for timeutils.
> 
> timeutils.cc uses timeGetTime, which is from winmm.
> 
> Bug: None
> Change-Id: I8e40f1c01c1128a80e9b5c59c0b28d39b3d0893a
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/128521
> Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
> Commit-Queue: Oleh Prypin <oprypin@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#27172}

TBR=mbonadei@webrtc.org,oprypin@webrtc.org,noahric@chromium.org

Change-Id: I3a648f694557b2a69a02682b5d0901193b13ac9c
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: None
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/128562
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Commit-Queue: Sam Zackrisson <saza@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27175}
diff --git a/rtc_base/BUILD.gn b/rtc_base/BUILD.gn
index ffa43bb..a396a63 100644
--- a/rtc_base/BUILD.gn
+++ b/rtc_base/BUILD.gn
@@ -410,10 +410,6 @@
     ":safe_conversions",
     ":stringutils",
   ]
-  libs = []
-  if (is_win) {
-    libs += [ "winmm.lib" ]
-  }
 }
 
 rtc_source_set("stringutils") {