Fix ffmpeg build (#15499)

ffmpeg needs a more recent meson. Meson now works with OSS-Fuzz again.

Author: jonathanmetzman

projects/ffmpeg/Dockerfile

@@ -20,8 +20,7 @@ RUN curl -LO https://mirrors.kernel.org/ubuntu/pool/main/a/automake-1.16/automak
     apt install ./automake_1.16.5-1.3_all.deb
 RUN curl -LO https://mirrors.kernel.org/ubuntu/pool/main/a/autoconf/autoconf_2.72-3.1ubuntu1_all.deb && \
     apt install ./autoconf_2.72-3.1ubuntu1_all.deb
-# Meson is pinned to get around https://github.com/mesonbuild/meson/issues/14533
-RUN python3 -m pip install --upgrade pip && python3 -m pip install -U meson==1.7.2 ninja
+RUN python3 -m pip install --upgrade pip && python3 -m pip install -U meson==1.11.1 ninja
 
 RUN git clone --depth 1 https://github.com/FFmpeg/FFmpeg ffmpeg