Fix extra whitespace in code block

[reakaleek]

Context

To reproduce, go to https://elastic.github.io/docs-builder/syntax/code.html#asciidoc-syntax
and copy the code using the copy button on the top-right corner.

If you paste the code somewhere, it will show like this (first line has extra whitespaces)

			[source,sh]
--------------------------------------------------
GET _tasks
GET _tasks?nodes=nodeId1,nodeId2
GET _tasks?nodes=nodeId1,nodeId2&actions=cluster:*
--------------------------------------------------

Changes

Fix the template to not add extra white space to the code block.

How to test

Open https://docs-v3-preview.elastic.dev/elastic/docs-builder/pull/410/syntax/code.html and copy any code block and paste it somewhere.