Update libvpx to 1.14.1.

Telegram/build/docker/centos_env/Dockerfile

@@ -172,7 +172,7 @@ FROM builder AS libvpx
 RUN git init libvpx \
 	&& cd libvpx \
 	&& git remote add origin {{ GIT }}/webmproject/libvpx.git \
-	&& git fetch --depth=1 origin 51057f4ba894e13f9bba278905bacf6aaaecd992 \
+	&& git fetch --depth=1 origin 12f3a2ac603e8f10742105519e0cd03c3b8f71dd \
 	&& git reset --hard FETCH_HEAD \
 	&& CFLAGS="$CFLAGS -fno-lto" CXXFLAGS="$CXXFLAGS -fno-lto" ./configure \
 		--disable-examples \

Telegram/build/prepare/prepare.py

@@ -983,7 +983,7 @@ stage('libvpx', """
     git clone https://github.com/webmproject/libvpx.git
 depends:patches/libvpx/*.patch
     cd libvpx
-    git checkout 51057f4ba8
+    git checkout v1.14.1
 win:
     for /r %%i in (..\\patches\\libvpx\\*) do git apply %%i