Bump Gitaly to 1.70.0 and remove cache invalidation feature flag

What does this MR do?

This change upgrades Gitaly to v1.70.0. Among other things, this removes the feature flag gitaly_cache_invalidator from Gitaly and GitLab as part of gitaly#1860 (closed).

Complete list of changes in Gitaly changelog (Note: small error in changelog due to invalid version string vv1.70.0 present):

v1.70.0

Added

• Lower gRPC server inactivity ping timeout gitaly!1294 (merged)

Other

• Remove RepositoryService WriteConfig gitaly!1558 (merged)
• Refactor praefect server tests gitaly!1554 (merged)

v1.69.0

Fixed

• Fix praefect server info to include git version, server version gitaly!1550 (merged)

Other

• Enable second repository to have its storage re-written gitaly!1548 (merged)

v1.68.0

Added

• Add virtual storage name to praefect config gitaly!1525 (merged)
• Support health checks in Praefect gitaly!1541 (merged)

Changed

• Provide specifics about why a cherry-pick or revert has failed gitaly!1543 (merged)

Other

• Upgrade GRPC to 1.24.0 gitaly!1539 (merged)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

Test coverage handled in the Gitaly project.