GUACAMOLE-773: Update Java dependencies to latest stable, compatible versions.

doc/licenses/cas-client-3.6.4/NOTICE

@@ -0,0 +1,2 @@
+This project includes:
+  Jasig CAS Client for Java - Core under Apache License Version 2.0

doc/licenses/cas-client-3.6.4/README

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+Java Apereo CAS Client (https://www.apereo.org/projects/cas)
+------------------------------------------------------------
+
+    Version: 3.6.4
+    From: 'Apereo Foundation' (https://www.apereo.org/)
+    License(s):
+        Apache v2.0
+

doc/licenses/cas-client-3.6.4/dep-coordinates.txt

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+org.jasig.cas.client:cas-client-core:jar:3.6.4