Merge 21.6 code freeze into trunk with conflicts resolutions

[mokagio]

See #19964 description.

We got conflicts on Podfile.lock checksum because both trunk and release/21.6 changed Podfile.

• trunk with b146b82
• release/21.6 with 018a5e1

I resolved the conflicts by re-running bundle exec pod install to generated a new checksum field.

Since this PR differs from #19964 only in fixing the Podfile.lock checksum conflict, I'm going to consider the approval on #19964 as approval for this one too, and admin merge.

[peril-wordpress-mobile]

	Warnings
⚠️	The AppStoreStrings.po file must be updated any time changes are made to release notes
⚠️	Localizable.strings should only be updated on release branches because it is generated automatically.
⚠️	PR is not assigned to a milestone.
⚠️	PR is missing at least one label.

Generated by 🚫 dangerJS

[wpmobilebot]

You can test the changes in WordPress from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr19973-53ff2f9 on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[wpmobilebot]

You can test the changes in Jetpack from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr19973-53ff2f9 on your iPhone

If you need access to App Center, please ask a maintainer to add you.