undo removing "a"

Co-authored-by: Dave Thaler <[email protected]>

draft-ietf-rats-endorsements.md

@@ -98,7 +98,7 @@ Target Environments and Attesting Environments that are components of an Atteste
 "Actual state" is a group of claim sets about the actual state of the Attester at a
 given point in time. Each claim set holds claims about a specific Target Environment
 that is essential to determining trustworthiness.  Generally speaking, each claim
-has a name (typically referred to as label, and occasionally referred to as key or code-point)
+has a name (typically referred to as a label, and occasionally referred to as a key or code-point)
 and a singleton value, being a value collected from a Target Environment of a specific Attester at a given point
 in time. Some claims may inherently have multiple values, such as a list of
 files in a given location on the device, but in the context of this document such