Bug 37342: Use get for launching authority popup

This patch simply switches to a GET as the operation is not cud

To test:
 1 - Go to cataloging -> new record
 2 - If not in basic editor, switch
 3 - Go to tab 100
 4 - Enter a name that has no authority in your system: McNotExist, Falsy
 5 - Click 'Link authorities automatically'
 6 - subfield 9 should turn red, and have an X and a + button
 7 - Click the green +
 8 - Boom
 9 - Apply patch
10 - Reload page and repeat (clear cache so js reloads)
11 - Success! Authority window launches

Signed-off-by: Jake Deery <jake.deery@ptfs-europe.com>
Signed-off-by: Emily Lamancusa <emily.lamancusa@montgomerycountymd.gov>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>

koha-tmpl/intranet-tmpl/prog/en/modules/cataloguing/addbiblio.tt

@@ -266,7 +266,7 @@ function addCreateAuthorityButton(tag_subfield_line, heading, tag_index) {
         if(popup !== null) {
             // Create a new form that will be POSTed in the new window
             var form = $('<form>').attr({
-            method: 'post',
+            method: 'get',
             action: "/cgi-bin/koha/authorities/authorities.pl",
             target: "new_auth_popup"
             });