GUACAMOLE-1905: Update JDBC driver versions in Dockerfile.

Dockerfile

@@ -52,8 +52,8 @@ ARG MAVEN_ARGUMENTS="-DskipTests=false"
 
 # Versions of JDBC drivers to bundle within image
 ARG MSSQL_JDBC_VERSION=9.4.1
-ARG MYSQL_JDBC_VERSION=8.0.33
-ARG PGSQL_JDBC_VERSION=42.6.0
+ARG MYSQL_JDBC_VERSION=8.3.0
+ARG PGSQL_JDBC_VERSION=42.7.2
 
 # Build environment variables
 ENV \