ffmpeg: update autoconf to 2.72 to fix build

Needed after https://gitlab.xiph.org/xiph/theora/-/commit/34bf876678f87614ebe24d78c037601d9e01052e

Author: kasper93

projects/ffmpeg/Dockerfile

@@ -15,9 +15,11 @@
 ################################################################################
 
 FROM gcr.io/oss-fuzz-base/base-builder
-RUN apt-get update && apt-get install -y nasm pkg-config rsync autoconf libtool gperf
+RUN apt-get update && apt-get install -y nasm pkg-config rsync libtool gperf
 RUN curl -LO https://mirrors.kernel.org/ubuntu/pool/main/a/automake-1.16/automake_1.16.5-1.3_all.deb && \
     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_all.deb && \
+    apt install ./autoconf_2.72-3_all.deb
 RUN python3 -m pip install --upgrade pip && python3 -m pip install -U meson ninja
 
 RUN git clone https://git.ffmpeg.org/ffmpeg.git ffmpeg