[css-grid] Remove stray references to grid-gap. Fixes w3c#1785.

Author: fantasai

css-grid/Overview.bs

@@ -26,7 +26,6 @@ Abstract: This CSS module defines a two-dimensional grid-based layout system, op
 Ignored Terms: containing block, <positive-integer>, <ident>, auto, grid-*-start, grid-*-end, flex factor, flex factors, block formatting context, grid-auto-position, min size property, max size property
 Ignored Vars: A, B, C, size-contribution, track-sizes, extra-space
 Link Defaults: css21 (property) margin/min-height/max-height/min-width/max-width, css-align-3 (value) stretch/baseline, css-position-3 (property) left, css-position-3 (property) position, css-writing-modes-3 (dfn) start/end
-At Risk: the <<percentage>> value in 'grid-row-gap'/'grid-column-gap' (low priority)
 At Risk: application of grid placement to absolutely-positioned boxes
 </pre>
 
@@ -1512,7 +1511,7 @@ Explicit Track Sizing: the 'grid-template-rows' and 'grid-template-columns' prop
 	</div>
 
 	Note: The size of the grid is not purely the sum of the track sizes,
-	as 'grid-row-gap', 'grid-column-gap' and  'justify-content', 'align-content'
+	as 'row-gap', 'column-gap' and 'justify-content', 'align-content'
 	can add additional space between tracks.
 
 <!--
@@ -1638,7 +1637,7 @@ Repeat-to-fill: ''auto-fill'' and ''auto-fit'' repetitions</h5>
 	that does not cause the <a>grid</a> to overflow its <a>grid container</a>
 	(treating each track as its <a>max track sizing function</a> if that is <a>definite</a>
 	or as its minimum track sizing function otherwise,
-	and taking 'grid-gap' into account);
+	and taking 'gap' into account);
 	if any number of repetitions would overflow,
 	then 1 repetition.
 	Otherwise, if the <a>grid container</a> has a <a>definite</a> min size in the relevant axis,
@@ -3372,7 +3371,7 @@ Aligning the Grid: the 'justify-content' and 'align-content' properties</h3>
 			  display: grid;
 			  /* 3-row / 4-column grid container */
 			  grid: repeat(3, auto) / repeat(4, auto);
-			  grid-gap: 10px;
+			  gap: 10px;
 			  align-content: space-around;
 			  justify-content: space-between;
 			}
@@ -3396,7 +3395,7 @@ Aligning the Grid: the 'justify-content' and 'align-content' properties</h3>
 			<figcaption>Grid after alignment</figure>
 		</figure>
 
-		Note that alignment (unlike 'grid-gap' spacing)
+		Note that alignment (unlike 'gap' spacing)
 		happens after the grid tracks are sized,
 		so if the track sizes are determined by the contents of the spanned item,
 		it will gain excess space in the alignment stage