build(travis): Use :latest tag for getsentry/sentry (#252)

install.sh

@@ -1,8 +1,6 @@
 #!/usr/bin/env bash
 set -e
 
-LATEST_STABLE_SENTRY_IMAGE='sentry:9.1.2'
-
 MIN_DOCKER_VERSION='17.05.0'
 MIN_COMPOSE_VERSION='1.17.0'
 MIN_RAM=3072 # MB
@@ -57,12 +55,6 @@ else
   cp -n .env.example "$ENV_FILE"
 fi
 
-if [ -z $SENTRY_IMAGE ]; then
-  echo ""
-  echo "\$SENTRY_IMAGE not set, using latest stable: $LATEST_STABLE_SENTRY_IMAGE";
-  export SENTRY_IMAGE=$LATEST_STABLE_SENTRY_IMAGE
-fi
-
 echo ""
 echo "Building and tagging Docker images..."
 echo ""