Bump default theme versions for WordPress 5.9

[desrosj]

The release of 5.9 will be accompanied by a release for all default themes. The new versions are as follows:

Twenty Twenty-One: 1.5
Twenty Twenty: 1.9
Twenty Nineteen: 2.2
Twenty Seventeen: 2.9
Twenty Sixteen: 2.6
Twenty Fifteen: 3.1
Twenty Fourteen: 3.3
Twenty Thirteen: 3.5
Twenty Twelve: 3.6
Twenty Eleven: 4.0
Twenty Ten: 3.6

Previously:

• #53277 - 5.8
• #52704 - 5.7
• #51919 - 5.6
• #50889 - 5.5
• #49743 - 5.4

Trac ticket: https://core.trac.wordpress.org/ticket/54783

[audrasjb]

Patch readme to ship.
I also updated a wrong Codex version link for the previous release of Twenty Twelve.

[audrasjb]

Self-assigning. As per previous releases, this should be committed to trunk right before the 5.9 code freeze, then backported to branch 5.9.

[desrosj]

Reassigning to myself. I offered to tackle this since I'll also be uploading the new theme versions on release day.

[hellofromTonya]

Looks good for commit to trunk and backport to 5.9-branch.

[desrosj]

In 52618:

Bundled Themes: Bump the versions for bundled themes for release.

This bumps the versions of the default bundled themes in preparation for release with WordPress 5.9.

The new versions are:

• Twenty Ten: 3.6
• Twenty Eleven: 4.0
• Twenty Twelve: 3.6
• Twenty Thirteen: 3.5
• Twenty Fourteen: 3.3
• Twenty Fifteen: 3.1
• Twenty Sixteen: 2.6
• Twenty Seventeen: 2.9
• Twenty Nineteen: 2.2
• Twenty Twenty: 1.9
• Twenty Twenty-One: 1.5

Props audrasjb.
Fixes #54783.

[desrosj]

Reopening to backport.

Merged in https://core.trac.wordpress.org/changeset/52618.

[desrosj]

In 52619:

Bundled Themes: Bump the versions for bundled themes for release.

This bumps the versions of the default bundled themes in preparation for release with WordPress 5.9.

The new versions are:

• Twenty Ten: 3.6
• Twenty Eleven: 4.0
• Twenty Twelve: 3.6
• Twenty Thirteen: 3.5
• Twenty Fourteen: 3.3
• Twenty Fifteen: 3.1
• Twenty Sixteen: 2.6
• Twenty Seventeen: 2.9
• Twenty Nineteen: 2.2
• Twenty Twenty: 1.9
• Twenty Twenty-One: 1.5

Props audrasjb.
Merges [52618] to the 5.9 branch
Fixes #54783.