Update to MG5aMC_PY8_INTERFACE_VERSION=1.3 as 1.2 is gone

Author: matthewfeickert

docker/centos/Dockerfile

@@ -136,7 +136,7 @@ RUN mkdir -p /code && \
 ARG MG_VERSION=3.4.1
 # Versions viewable on Illinois mirror
 # http://madgraph.physics.illinois.edu/Downloads/MG5aMC_PY8_interface/
-ARG MG5aMC_PY8_INTERFACE_VERSION=1.2
+ARG MG5aMC_PY8_INTERFACE_VERSION=1.3
 RUN cd /usr/local/venv && \
     wget --quiet https://launchpad.net/mg5amcnlo/3.0/3.4.x/+download/MG5_aMC_v${MG_VERSION}.tar.gz && \
     mkdir -p /usr/local/venv/MG5_aMC && \

docker/debian/Dockerfile

@@ -127,7 +127,7 @@ RUN mkdir /code && \
 ARG MG_VERSION=3.4.1
 # Versions viewable on Illinois mirror
 # http://madgraph.physics.illinois.edu/Downloads/MG5aMC_PY8_interface/
-ARG MG5aMC_PY8_INTERFACE_VERSION=1.2
+ARG MG5aMC_PY8_INTERFACE_VERSION=1.3
 RUN cd /usr/local/venv && \
     wget --quiet https://launchpad.net/mg5amcnlo/3.0/3.4.x/+download/MG5_aMC_v${MG_VERSION}.tar.gz && \
     mkdir -p /usr/local/venv/MG5_aMC && \