GUACAMOLE-1594: Update Java dependencies to latest compatible versions.

doc/licenses/kotlin-1.8.0/NOTICE.txt

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+Kotlin Compiler
+Copyright 2010-2020 JetBrains s.r.o and respective authors and developers

doc/licenses/kotlin-1.8.0/README

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+Kotlin (https://kotlinlang.org/)
+--------------------------------
+
+    Version: 1.8.0
+    From: 'JetBrains s.r.o and respective authors and developers'
+    License(s):
+        Apache v2.0
+

doc/licenses/kotlin-1.8.0/dep-coordinates.txt

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+org.jetbrains.kotlin:kotlin-reflect:jar:1.8.0
+org.jetbrains.kotlin:kotlin-stdlib:jar:1.8.0
+org.jetbrains.kotlin:kotlin-stdlib-common:jar:1.8.0
+org.jetbrains.kotlin:kotlin-stdlib-jdk8:jar:1.8.0
+org.jetbrains.kotlin:kotlin-stdlib-jdk7:jar:1.8.0