[css-text-4] Rename trim-inner to discard-inner for consistency w3c#448

Author: fantasai

css-text-4/Overview.bs

@@ -2569,7 +2569,7 @@ White Space Collapsing: the 'text-space-collapse' property</h3>
 				text-space-collapse: discard;
 			}
 			m|mi, m|mn, m|mo, m|ms, m|mtext {
-				text-space-trim: trim-inner;
+				text-space-trim: discard-inner;
 			}
 		</pre>
 	</div>
@@ -2579,7 +2579,7 @@ White Space Trimming: the 'text-space-trim' property</h3>
 
 	<pre class="propdef">
 	Name: text-space-trim
-	Value: none | trim-inner || discard-before || discard-after
+	Value: none | discard-inner || discard-before || discard-after
 	Initial: none
 	Applies to: [=inline boxes=] and [=block containers=]
 	Inherited: no
@@ -2594,7 +2594,7 @@ White Space Trimming: the 'text-space-trim' property</h3>
 	which must be interpreted according to the white space processing rules:
 
 	<dl dfn-for=text-space-trim dfn-type=value>
-		<dt><dfn>trim-inner</dfn>
+		<dt><dfn>discard-inner</dfn>
 		<dd>
 			For block containers this value directs UAs to discard
 			all whitespace at the beginning of the element up to and including