Remove calls to `Range.detach`

This method is a no-op, as demonstrated by console warnings in Chrome and https://developer.mozilla.org/en-US/docs/Web/API/range.detach.

Remove callsites.

Fixes #2142

src/browser/ui/ReactDOMSelection.js

@@ -114,7 +114,6 @@ function getModernOffsets(node) {
   detectionRange.setStart(anchorNode, anchorOffset);
   detectionRange.setEnd(focusNode, focusOffset);
   var isBackward = detectionRange.collapsed;
-  detectionRange.detach();
 
   return {
     start: isBackward ? end : start,
@@ -194,8 +193,6 @@ function setModernOffsets(node, offsets) {
       range.setEnd(endMarker.node, endMarker.offset);
       selection.addRange(range);
     }
-
-    range.detach();
   }
 }