Fix release version on doc for epic date sourcing / new epic notification

Due to features missing 11.2 deadline, they are in 11.3 instead. However the documentation still states that the features are available since 11.2, hence this fix.

• Documents Add date fields to Epic to enable dates to source from milestones
• Documents Resolve "Customize notifications for new epic - Web and API"
• Follow-up from: #XXX, !YYY

New doc or update?

• New documentation
• Update existing documentation

Checklists

Product Manager

A small change so PM can be skipped

• Add the correct labels
• Add the correct milestone
• Indicate the correct document/directory for this feature
• Fill the doc blurb below

Developer

• Copy the doc blurb above and paste it into the doc
• Write the tutorial - explain how to use the feature
• Submit the MR using the appropriate MR description template