chore: remove old patch for fixing ffmpeg on 32-bit linux (#15226)

It's no longer necessary, per the comment

patches/common/ffmpeg/.patches

@@ -1,2 +1 @@
 build_gn.patch
-fix_build_on_linux_x86.patch

patches/common/ffmpeg/fix_build_on_linux_x86.patch

@@ -1,21 +0,0 @@
-From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
-From: Aleksei Kuzmin <alkuzmin@microsoft.com>
-Date: Mon, 22 Oct 2018 10:45:25 -0700
-Subject: fix_build_on_linux_x86.patch
-
-Builds on Linux x86 fail with a clang error. See https://crbug.com/796379.
-Once it's fixed the patch can be removed.
-
-diff --git a/BUILD.gn b/BUILD.gn
-index 947deba96107c931582007ce89917f8896923a6f..7afd535cb5e43762a14c51dd7b3b163571958d9c 100755
---- a/BUILD.gn
-+++ b/BUILD.gn
-@@ -239,7 +239,7 @@ target(link_target_type, "ffmpeg_internal") {
-   # Windows builds can't compile without EBP because we can't omit frame
-   # pointers like we do on posix.
-   if (target_cpu == "x86") {
--    if (using_sanitizer || is_win) {
-+    if (using_sanitizer || is_win || is_electron_build) {
-       defines += [ "HAVE_EBP_AVAILABLE=0" ]
-     } else {
-       defines += [ "HAVE_EBP_AVAILABLE=1" ]