[DOCS] Alerts related by session ID and Alerts related by process ancestry no longer beta and don't require a feature flag

[nastasha-solomon]

Description

Several changes are happening within the Alerts related by process ancestry within the Insights section:

• No longer behind a feature flag
• License requirement - Platinum or Enterprise subscription
• The beta tag will be removed from the section since the feature is GA'ing in 8.5.

Minor changes to the Alerts related by session insights section:

• Feature is no longer behind a feature flag.
• License requirement - Enterprise subscription
• The beta tag is being removed since the feature is going GA.

Related issues/PRs

• [SecuritySolution] Move related alerts by process ancestry behind platinum subscription kibana#138419
• [SecuritySolution] Enable prevalence by process ancestry by default kibana#140006

Doc updates

• Refresh screenshot (insights-section.png) in the Insights on alerts section.
  • IMPORTANT: Might need to hold off on refreshing this screenshot because will be doing the same in [DOCS] Host and user risk score alert enrichments #2480)
• Remove beta tags in the descriptions for the Alerts related by process ancestry and Alerts related by session insights sections.