Updated WeakTLSProtocol related rules

What does this MR do?

• This rule was split into two files:
  • rule-WeakTLSProtocol-DefaultHttpClient
  • rule-WeakTLSProtocol-SSLContext
• For SSLContext.getInstance, remediation text created.
• For DefaultHttpClient, the references to SSLContext removed.
• Updated the mappings file accordingly

What are the relevant issue numbers?

Issue - gitlab-org/gitlab#433049 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
  • Auto-DevOps template
  • Job definition example
  • CI Templates
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer