README: update backtick usage

Adrian Kirchner · Adrian Kirchner · commit ecb2340b110f · 2018-10-23T13:12:32.000+02:00
diff --git a/README.md b/README.md
@@ -53,4 +53,4 @@ classes:
 
 When making changes you can test this module locally with [gitlab-runner on Mac OSX](https://docs.gitlab.com/runner/install/osx.html)
 
-`gitlab-runner exec docker --env "GIT_STRATEGY=none" --docker-volumes `pwd`:/builds/project-0 xenial:puppet5`
+``gitlab-runner exec docker --env "GIT_STRATEGY=none" --docker-volumes `pwd`:/builds/project-0 xenial:puppet5``

Original file line number	Diff line number	Diff line change
`@@ -53,4 +53,4 @@ classes:`
`53`	`53`
`54`	`54`	`When making changes you can test this module locally with [gitlab-runner on Mac OSX](https://docs.gitlab.com/runner/install/osx.html)`
`55`	`55`
`56`		-`gitlab-runner exec docker --env "GIT_STRATEGY=none" --docker-volumes `pwd`:/builds/project-0 xenial:puppet5`
	`56`	+``gitlab-runner exec docker --env "GIT_STRATEGY=none" --docker-volumes `pwd`:/builds/project-0 xenial:puppet5``