Update xml.cson

[jurgen178]

Description of the Change

Fix tm regex for XML comment <%-- --%>. The end rule key and the name key are in the scope of the captures key, but should be up one level in the comments patterns.
The grammar file for xml in VS is

	"comments": {
		"patterns": [
			{
				"begin": "<%--",
				"captures": {
					"0": {
						"name": "punctuation.definition.comment.xml"
					},
					"end": "--%>",
					"name": "comment.block.xml"
				}

but should be:

	"comments": {
		"patterns": [
			{
				"begin": "<%--",
				"captures": {
					"0": {
						"name": "punctuation.definition.comment.xml"
					}
				},
				"end": "--%>",
				"name": "comment.block.xml"
			},

Repro:
Add the <%-- style comment patterns to a XML file.

<%--
This comment and all following content is not syntax colored.
--%>

All following lines are not processed for syntax coloring because the end rule key is missing for the comments patterns.

Test:
With the fixed regex, the comment will be correctly syntax colored as well as all the following xml content.

Requirements

• Filling out the template is required. Any pull request that does not include enough information to be reviewed in a timely manner may be closed at the maintainers' discretion.
• All new code requires tests to ensure against regressions

Alternate Designs

Benefits

Possible Drawbacks

Applicable Issues

[jurgen178]

Looks like this issue is reported multiple times before.
#96
#106