Fix available dimensions for rum.measure.session.action metric

[jasonscottdatadog]

What does this PR do? What is the motivation?

This PR fixes the documentation for the rum.measure.session.action metric by removing dimensions that are not actually available in the metric data.

Changes:

• Removed "Action Type" from the available dimensions list
• Removed "View Name" from the available dimensions list

Motivation:
These dimensions are not available for this metric. The metric only supports the Default dimensions (application.id, application.name, browser.name, env, geo.country, os.name, os.version, service, version).

Merge instructions

Merge readiness:

• Ready for merge

[github-actions]

Preview links (active after the build_preview check completes)

Modified Files

• https://docs-staging.datadoghq.com/jason.scott/fix-rum-session-action-dimensions/real_user_monitoring/rum_without_limits/metrics