Update dependency org.apache.struts:struts2-core to v6

[mend-for-github-com]

This PR contains the following updates:

Package	Type	Update	Change
org.apache.struts:struts2-core (source)	compile	major	2.3.12 → 6.8.0
org.apache.struts:struts2-core (source)	compile	major	2.3.8 → 6.8.0

By merging this PR, the below issues will be automatically resolved and closed:

Severity	CVSS Score	Vulnerability	GitHub Issue
Critical	9.8	CVE-2017-5638	#53
Critical	9.0	CVE-2024-53677	#-1
High	8.2	CVE-2025-66675	#-1
High	8.1	CVE-2025-68493	#-1
High	7.5	CVE-2025-64775	#-1

By merging this PR, the below issues will be automatically resolved and closed:

Severity	CVSS Score	Vulnerability	GitHub Issue
Critical	9.8	CVE-2017-5638	#53
Critical	9.0	CVE-2024-53677	#-1
High	8.2	CVE-2025-66675	#-1
High	8.1	CVE-2025-68493	#-1
High	7.5	CVE-2025-64775	#-1

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