doc: fix source link margin to sub-header mark

Prior to this commit, [src] link overlapped sharped (#) sub-header link

PR-URL: #33664
Reviewed-By: James M Snell <[email protected]>

Author: rodion-arr

doc/api_assets/style.css

@@ -342,6 +342,7 @@ h5 {
 .srclink {
   float: right;
   font-size: smaller;
+  margin-right: 30px;
 }
 
 h1 span,