Remove POSTGIS_VERSION env variable and run test using mvt renderer always

test/support/prepare_db.sh

@@ -73,20 +73,6 @@ echo "PUBLICPASS: ${PUBLICPASS}"
 echo "TESTUSER: ${TESTUSER}"
 echo "TESTPASS: ${TESTPASS}"
 
-# Sets the env variable POSTGIS_VERSION as Major * 10000 + Minor * 100 + Patch
-# For example, for 2.4.5 ~> 20405
-auto_postgis_version() {
-    local POSTGIS_STR=$(psql -c "Select default_version from pg_available_extensions WHERE name = 'postgis';" -t);
-    local pg_version=$(echo $POSTGIS_STR | awk -F '.' '{print $1 * 10000 + $2 * 100 + $3}')
-
-    echo $pg_version
-}
-
-if [ -z "$POSTGIS_VERSION" ]; then
-    export POSTGIS_VERSION=$(auto_postgis_version)
-    echo "POSTGIS_VERSION: ${POSTGIS_VERSION}"
-fi
-
 if test x"$PREPARE_PGSQL" = xyes; then
 
   echo "preparing postgres..."