Add missing word in sentence. (dotnet#1256)

The sentence "If you do not apply a  to a capturing group,.." is missing the word "quantifier" and should read "If you do not apply a QUANTIFIER to a capturing group,.."

Author: ericmutta

xml/System.Text.RegularExpressions/Capture.xml

@@ -42,7 +42,7 @@
 ## Remarks  
  A <xref:System.Text.RegularExpressions.Capture> object is immutable and has no public constructor. Instances are returned through the <xref:System.Text.RegularExpressions.CaptureCollection> object, which is returned by the `Match.Captures` and <xref:System.Text.RegularExpressions.Group.Captures%2A?displayProperty=nameWithType> properties. However, the `Match.Captures` property provides information about the same match as the <xref:System.Text.RegularExpressions.Match> object.  
   
- If you do not apply a  to a capturing group, the <xref:System.Text.RegularExpressions.Group.Captures%2A?displayProperty=nameWithType> property returns a <xref:System.Text.RegularExpressions.CaptureCollection> with a single <xref:System.Text.RegularExpressions.Capture> object that provides information about the same capture as the <xref:System.Text.RegularExpressions.Group> object. If you do apply a quantifier to a capturing group, the `Group.Index`, `Group.Length`, and `Group.Value` properties provide information only about the last captured group, whereas the <xref:System.Text.RegularExpressions.Capture> objects in the <xref:System.Text.RegularExpressions.CaptureCollection> provide information about all subexpression captures. The example provides an illustration.  
+ If you do not apply a quantifier to a capturing group, the <xref:System.Text.RegularExpressions.Group.Captures%2A?displayProperty=nameWithType> property returns a <xref:System.Text.RegularExpressions.CaptureCollection> with a single <xref:System.Text.RegularExpressions.Capture> object that provides information about the same capture as the <xref:System.Text.RegularExpressions.Group> object. If you do apply a quantifier to a capturing group, the `Group.Index`, `Group.Length`, and `Group.Value` properties provide information only about the last captured group, whereas the <xref:System.Text.RegularExpressions.Capture> objects in the <xref:System.Text.RegularExpressions.CaptureCollection> provide information about all subexpression captures. The example provides an illustration.  
   
    
   
@@ -284,4 +284,4 @@
       </Docs>
     </Member>
   </Members>
-</Type>
+</Type>