switch template for einfra from keycloak to specific provider

this avoids redirection proiblems that keycloak currently has in Galaxy

xref galaxyproject/galaxy#20688

Author: martenson

templates/galaxy/config/oidc_backends_config.xml.j2

@@ -1,11 +1,9 @@
 <?xml version="1.0"?>
 <OIDC>
-    <provider name="Keycloak">
-      <client_id>{{ einfracz_client_id }}</client_id>
-      <client_secret>{{ einfracz_client_secret }}</client_secret>
-      <redirect_uri>https://{{ inventory_hostname }}/authnz/keycloak/callback</redirect_uri>
-      <url>https://login.e-infra.cz/oidc</url>
-      <icon>https://www.e-infra.cz/img/logo.svg</icon>
-      <!-- <extra_scopes>offline_access</extra_scopes> -->
-    </provider>
+  <provider name="Einfracz">
+    <client_id>{{ einfracz_client_id }}</client_id>
+    <client_secret>{{ einfracz_client_secret }}</client_secret>
+    <redirect_uri>https://{{ inventory_hostname }}/authnz/einfracz/callback</redirect_uri>
+    <icon>https://www.e-infra.cz/img/logo.svg</icon>
+  </provider>
 </OIDC>