Check if testTemplatesSourceFolder is valid and needed

[jan-vcapgemini]

Check if this test is still needed:

https://github.com/devonfw/cobigen/blob/ac2efa9bf52a67f015d53d7a825b9cc0e9d5e399/cobigen/cobigen-core/src/test/java/com/devonfw/cobigen/unittest/config/reader/TemplatesConfigurationReaderTest.java#L93-L116