[Java] Use new location for hibernate validator

[Munken]

As per https://mvnrepository.com/artifact/org.hibernate/hibernate-validator
org.hibernate:hibernate-validator was renamed to org.hibernate.validator:hibernate-validator.

This PR adjust the pom templates to reflect this.

It also bumps the version to the 8 series, which coincide with the latest Spring BOM

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[wing328]

thanks for the pr

please follow step 3 to update the samples

[Munken]

@wing328 samples updated

[wing328]

thanks for the PR, which has been merged