Bundled Themes: Bump version number and update changelog in Twenty Seventeen for 4.9.5 release

[audrasjb]

Since 4.9.5 will probably ship a patch to address some accessibility/readability issues in Twenty Seventeen, let's add a Task to bump the version number and update the changelog.

Twenty Seventeen is the only concerned theme.
Related ticket: #43317

Handbook page: ​https://make.wordpress.org/core/handbook/about/release-cycle/update-bundled-themes/

Previous related tickets for reference:
4.9: #42090
4.8: #40905

Note: If #43317 is finally not shipped with 4.9.5, then this task may be closed.

[audrasjb]

Bump version number and update changelog in Twenty Seventeen for 4.9.5 release

[SergeyBiryukov]

In 42881:

Twenty Seventeen: Bump version and update the changelog.

Props audrasjb.
Fixes #43572.

[SergeyBiryukov]

In 42882:

Twenty Seventeen: Bump version and update the changelog.

Props audrasjb.
Merges [42881] to the 4.9 branch.
Fixes #43572.

[davidakennedy]

Just following up here to say I've updated the changelog: ​https://codex.wordpress.org/Twenty_Seventeen_Theme_Changelog#Version_1.5