Release 0.27.9

[stefanceriu]

This PR prepares the release of MatrixSDK v0.27.9.

Notes:

• This PR targets release/0.27.9/master, which has been cut from master.
• It includes changes to the Podfile, but not the corresponding changes to Podfile.lock, as pod install hasn't yet been run. This is because the Podfile targets future versions of dependencies yet to be released, so pod install wouldn't be able to find them yet.
• When the CI runs its checks, it will temporarily point to the pending release branches of those dependencies beforehand
• It is only during release:finish that pod update will be run -- updating the Podfile.lock to use the now officially released dependencies -- before ultimately merging release/0.27.9/master into master to tag the release.

---

➡️ Once this PR is merged, you will need to first ensure that the products this one depends on are fully released, then run bundle exec rake release:finish to close this release.

💡 If you want to review only the changes made since the release branch was cut from develop, you can check those here

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 16 lines in your changes missing coverage. Please review.

Please upload report for BASE (release/0.27.9/master@11aa1f4). Learn more about missing BASE report.

Files	Patch %	Lines
MatrixSDK/MXRestClient.m	0.00%	16 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## release/0.27.9/master #1860 +/- ## ======================================================== Coverage ? 35.66% ======================================================== Files ? 617 Lines ? 97105 Branches ? 41508 ======================================================== Hits ? 34636 Misses ? 61547 Partials ? 922 ```

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