Fix YAML metadata on "Understanding Concepts" (#1911)

SamB · Sean Wheeler · commit c6f3f13fce3a · 2017-12-01T17:04:10.000-08:00
I'm not quite sure what this means, but it certainly looks terrible on docs.microsoft.com when it's malformed.

(To be perfectly honest, I only managed to even figure out it's called "YAML metadata" by peeking at the DOM of github's HTML.)
diff --git a/reference/docs-conceptual/getting-started/understanding-concepts-reference.md b/reference/docs-conceptual/getting-started/understanding-concepts-reference.md
@@ -1,4 +1,4 @@
-.md---
+---
 ms.date:  2017-06-05
 keywords:  powershell,cmdlet
 title:  understanding concepts reference

Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-.md---`
	`1`	`+---`
`2`	`2`	`ms.date: 2017-06-05`
`3`	`3`	`keywords: powershell,cmdlet`
`4`	`4`	`title: understanding concepts reference`