Update get_plugins_xml

Adding 3.8 and 3.9 so they will be from cache (instead of live query). 
Also removed 1.8.
Did this also in the running Docker container (so no need to update running code there)

scripts/get_plugins_xml

@@ -14,7 +14,7 @@
 DEST_DIR="/home/plugins/cached_xmls/plugins"
 BASE_URL="http://plugins.qgis.org/plugins/plugins_new.xml"
 
-for VERSION in 1.8 2.0 2.2 2.4 2.6 2.8 2.10 2.12 2.14 2.15 2.16 2.17 2.18 2.99 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7; do
+for VERSION in 2.0 2.2 2.4 2.6 2.8 2.10 2.12 2.14 2.15 2.16 2.17 2.18 2.99 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9; do
     if [[ -f $DEST_DIR/plugins_${VERSION}.xml.temp ]]; then
         rm $DEST_DIR/plugins_${VERSION}.xml.temp
     fi