GUACAMOLE-773: Bring license details of bundled Java dependencies up-to-date.

doc/licenses/error-prone-2.5.1/README

@@ -0,0 +1,8 @@
+Error Prone (https://errorprone.info/)
+--------------------------------------
+
+    Version: 2.5.1
+    From: 'Google Inc.' (http://www.google.com/)
+    License(s):
+        Apache v2.0
+

doc/licenses/error-prone-2.5.1/maven-coordinates.txt

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+com.google.errorprone:error_prone_annotations:jar:2.5.1