Don't add trailing space to processing instructions

[anthonyvdotbe]

In #240 (comment) it was decided that:

we should never generate a space before the end of processing instruction

However, I just noticed that this was only resolved for the XML prolog, and not for any other processing instructions. For example <?m2e ignore?> in a pom.xml still formats with a trailing space: <?m2e ignore ?>. To resolve this issue, I guess it should be sufficient to delete this line.

[angelozerr]

@anthonyvdotbe you are right, could you create a PR for that by adjusting tests please.

[anthonyvdotbe]

@angelozerr I created the PR

[angelozerr]

Fixed by eclipse/lemminx#934