Revert "Pin Prettier plug-in version in GitHub action (#351)"

This reverts commit c44313b.

[prettier/plugin-xml](https://github.com/prettier/plugin-xml) restored support for the `xmlSelfClosingSpace` option with prettier/plugin-xml#300 for [v1.1.0](https://github.com/prettier/plugin-xml/blob/main/CHANGELOG.md#110---2021-09-26), which allows formatting checks to complete successfully.

This commit unpins the plug-in version now that the regression in prettier/plugin-xml#11 is resolved, so the latest version of the plug-in can once again be used.

Signed-off-by: Roger Sheen <roger@infotexture.net>

Author: infotexture

.github/workflows/prettier.yml

@@ -28,6 +28,6 @@ jobs:
           # This part is also where you can pass other options, for example:
           prettier_options: --write **/*.{css,dita*,json,md,scss,xml,yaml,yml}
           # Install Prettier XML plugin
-          prettier_plugins: '@prettier/plugin-xml@v0.13.1'
+          prettier_plugins: '@prettier/plugin-xml'
           # Runs the action in dry mode. Files wont get changed and the action fails if there are unprettified files.
           dry: true