add changelog for repo update-passphrase command (#4507)

<!-- PR description-->

add changelog for `corso repo Update-passphrase` command

#### Does this PR need a docs update or release note?

- [ ] ✅ Yes, it's included

#### Type of change

<!--- Please check the type of change your PR introduces: --->
- [ ] 🗺️ Documentation

#### Issue(s)

<!-- Can reference multiple issues. Use one of the following "magic words" - "closes, fixes" to auto-close the Github issue. -->
* https://github.com/alcionai/corso/issues/4061

#### Test Plan

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CHANGELOG.md

@@ -19,6 +19,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Skips graph calls for expired item download URLs.
 - Export operation now shows the stats at the end of the run
+- Added `corso repo update-passphrase --new-passphrase` command to update the passphrase of existing Corso 
+repo.
 
 ### Fixed
 - Catch and report cases where a protected resource is locked out of access.  SDK consumers have a new errs sentinel that allows them to check for this case.

website/sidebars.js

@@ -53,6 +53,7 @@ const sidebars = {
             'cli/corso-repo-init-filesystem',
             'cli/corso-repo-connect-filesystem',
             'cli/corso-repo-maintenance',
+            'cli/corso-repo-update-passphrase',
             'cli/corso-env']
         },
         {