[css-values][css-values-3] Fix bikeshed linking error (ambiguous for-less link).

This causes correct linking of the resolution units, which previously
failed because these units were also defined in the css3-images draft
that is still the current TR draft.

Author: dbaron

css-values-3/Overview.bs

@@ -1301,7 +1301,7 @@ Frequency Units: the <<frequency>> type and ''Hz'', ''kHz'' units</h3>
 -->
 
 <h3 id="resolution">
-Resolution Units: the <<resolution>> type and ''dpi'', ''dpcm'', ''dppx'' units</h3>
+Resolution Units: the <<resolution>> type and ''&lt;resolution&gt;/dpi'', ''&lt;resolution&gt;/dpcm'', ''&lt;resolution&gt;/dppx'' units</h3>
 
 	Resolution units are <a>dimensions</a> denoted by <dfn id="resolution-value">&lt;resolution></dfn>.
 	The resolution unit identifiers are:
@@ -1323,7 +1323,7 @@ Resolution Units: the <<resolution>> type and ''dpi'', ''dpcm'', ''dppx'' units<
 	or the 'image-resolution' property defined in [[CSS3-IMAGES]].
 
 	All <<resolution>> units are <a>compatible</a>,
-	and ''dppx'' is their <a>canonical unit</a>.
+	and ''&lt;resolution&gt;/dppx'' is their <a>canonical unit</a>.
 
 	<div class="example">
 		The following @media rule uses Media Queries [[MEDIAQ]]

css-values/Overview.bs

@@ -1360,7 +1360,7 @@ Frequency Units: the <<frequency>> type and ''Hz'', ''kHz'' units</h3>
 -->
 
 <h3 id="resolution">
-Resolution Units: the <<resolution>> type and ''dpi'', ''dpcm'', ''dppx'' units</h3>
+Resolution Units: the <<resolution>> type and ''&lt;resolution&gt;/dpi'', ''&lt;resolution&gt;/dpcm'', ''&lt;resolution&gt;/dppx'' units</h3>
 
 	Resolution units are <a>dimensions</a> denoted by <dfn id="resolution-value">&lt;resolution></dfn>.
 	The resolution unit identifiers are:
@@ -1382,7 +1382,7 @@ Resolution Units: the <<resolution>> type and ''dpi'', ''dpcm'', ''dppx'' units<
 	or the 'image-resolution' property defined in [[CSS3-IMAGES]].
 
 	All <<resolution>> units are <a>compatible</a>,
-	and ''dppx'' is their <a>canonical unit</a>.
+	and ''&lt;resolution&gt;/dppx'' is their <a>canonical unit</a>.
 
 	<div class="example">
 		The following @media rule uses Media Queries [[MEDIAQ]]