[css-backgrounds-3] Drop nbsp from table headers. Fixes w3c#2911

Author: fantasai

css-backgrounds-3/Overview.bs

@@ -1593,7 +1593,7 @@ the padding is less than the radius of the corner.
       <th>Initial:
       <td>medium
     <tr>
-      <th>Applies&nbsp;to:
+      <th>Applies to:
       <td>all elements
     <tr>
       <th>Inherited:
@@ -1602,7 +1602,7 @@ the padding is less than the radius of the corner.
       <th>Percentages:
       <td>N/A
     <tr>
-      <th>Computed&nbsp;value:
+      <th>Computed value:
       <td>absolute length; zero if the border style is ''border-style/none'' or ''hidden''
     <tr>
       <th>Animatable:
@@ -1620,7 +1620,7 @@ the padding is less than the radius of the corner.
       <th>Initial:
       <td>(see individual properties)
     <tr>
-      <th>Applies&nbsp;to:
+      <th>Applies to:
       <td>all elements
     <tr>
       <th>Inherited:
@@ -1629,7 +1629,7 @@ the padding is less than the radius of the corner.
       <th>Percentages:
       <td>see individual properties
     <tr>
-      <th>Computed&nbsp;value:
+      <th>Computed value:
       <td>see individual properties
     <tr>
       <th>Animatable: