Documented the legacy healthcheck and tabletgateway and added summary…

… to 14's summary (#10567)

* Documented the legacy healthcheck and tabletgateway and added summary to 14_summary

Signed-off-by: Florent Poinsard <florent.poinsard@outlook.fr>

* Revert unwanted change in 14_summary

Signed-off-by: Florent Poinsard <florent.poinsard@outlook.fr>

doc/releasenotes/14_0_0_summary.md

@@ -1,3 +1,20 @@
+## Summary
+
+- [Gen4 is now the default planner](#gen4-is-now-the-default-planner)
+- [New query support](#new-query-support)
+- [Command-line syntax deprecations](#command-line-syntax-deprecations)
+- [New command line flags and behavior](#new-command-line-flags-and-behavior)
+- [Online DDL changes](#online-ddl-changes)
+- [Table lifecycle](#table-lifecycle)
+- [Tablet throttler](#tablet-throttler)
+- [New Syntax](#new-syntax)
+- [Heartbeat](#heartbeat)
+- [VDiff2](#vdiff2)
+- [Durability Policy](#durability-policy)
+- [Deprecation of Durability Configuration](#deprecation-of-durability-configuration)
+- [Advisory locking optimisations](#advisory-locking-optimisations)
+- [Drop the use of the legacy healthcheck in VTCtld](#drop-the-use-of-the-legacy-healthcheck-in-vtctld)
+
 ## Major Changes
 
 ### Gen4 is now the default planner
@@ -95,6 +112,10 @@ The flag `--online_ddl_check_interval` is deprecated and will be removed in `v15
 
 The flag `--planner-version` is deprecated and will be removed in `v15`. Instead, please use `--planer_version`.
 
+#### Removal of --gateway_implementation
+
+In previous releases, the `discoverygateway` was deprecated. In Vitess 14 it is now entirely removed, along with the VTGate flag that allowed us to select the tablet gateway.
+
 ### Online DDL changes
 
 #### Online DDL is generally available
@@ -289,4 +310,7 @@ the command `SetKeyspaceDurabilityPolicy` specified above, to ensure VTOrc conti
 path is to upgrade vtctld, run `SetKeyspaceDurabilityPolicy` and then upgrade VTOrc.**
 
 ### Advisory locking optimisations
-Work has gone into making the advisory locks (`get_lock()`, `release_lock()`, et al) release reserved connections faster and in more situations than before.
+Work has gone into making the advisory locks (`get_lock()`, `release_lock()`, et al) release reserved connections faster and in more situations than before.
+
+### Drop the use of the legacy healthcheck in VTCtld
+In release `7.0.0`, a new healthcheck was developed and the old one was renamed legacy healthcheck. In Vitess 14, we have changed VTCtld to use the new healthcheck instead of the legacy.