[JAVA-CAMEL] revert broken xml change

[martin-mfg]

#18870 broke the java-camel samples. see #18870 (comment) . In this PR I revert the problematic change.

java-camel re-uses the pojo.mustache file from JavaSpring. Since the mentioned change only breaks the java-camel sample but not the JavaSpring sample, I copied pojo.mustache from JavaSpring to java-camel and reverted the relevant change only there; not for JavaSpring.

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