Update 0039-use-apache-velocity-as-template-engine.md (#12187)

* Update 0039-use-apache-velocity-as-template-engine.md

* Update docs/decisions/0039-use-apache-velocity-as-template-engine.md

Co-authored-by: Subhramit Basu Bhowmick <subhramit.bb@live.in>

---------

Co-authored-by: Christoph <siedlerkiller@gmail.com>
Co-authored-by: Subhramit Basu Bhowmick <subhramit.bb@live.in>

docs/decisions/0039-use-apache-velocity-as-template-engine.md

@@ -54,6 +54,7 @@ ${CanonicalBibEntry.getCanonicalRepresentation($entry)}
 * Good, because it has simple syntax, and it is designed for simple template workflows.
 * Good, because it has a stable syntax ([source](https://stackoverflow.com/a/1984458/10037342)).
 * Bad, because it is in maintenance mode.
+* Bad, because [removed from Spring 5.0.1](https://www.baeldung.com/spring-template-engines#other-template-engines)
 
 ### Apache FreeMarker
 
@@ -107,4 +108,7 @@ Here are the papers you are analyzing:
 
 As stated in [the template discussion issue](https://github.com/koppor/jabref/issues/392), we should choose a template engine, and then slowly migrate previous code and templates to the chosen engine.
 
+Other template engines are discussed at <https://www.baeldung.com/spring-template-engines>, especially [`#other-template-engines`](https://www.baeldung.com/spring-template-engines#other-template-engines).
+We did not find any other engine there worth switching to.
+
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