help: use Windows cmd compatible quoting in revset help

mercurial/help/revsets.txt

@@ -178,26 +178,26 b' Some sample queries:'
 
 - Changesets on the default branch::
 
-    hg log -r 'branch(default)'
+    hg log -r "branch(default)"
 
 - Changesets on the default branch since tag 1.5 (excluding merges)::
 
-    hg log -r 'branch(default) and 1.5:: and not merge()'
+    hg log -r "branch(default) and 1.5:: and not merge()"
 
 - Open branch heads::
 
-    hg log -r 'head() and not closed()'
+    hg log -r "head() and not closed()"
 
 - Changesets between tags 1.3 and 1.5 mentioning "bug" that affect
   ``hgext/*``::
 
-    hg log -r '1.3::1.5 and keyword(bug) and file("hgext/*")'
+    hg log -r "1.3::1.5 and keyword(bug) and file('hgext/*')"
 
 - Changesets in committed May 2008, sorted by user::
 
-    hg log -r 'sort(date("May 2008"), user)'
+    hg log -r "sort(date('May 2008'), user)"
 
 - Changesets mentioning "bug" or "issue" that are not in a tagged
   release::
 
-    hg log -r '(keyword(bug) or keyword(issue)) and not ancestors(tagged())'
+    hg log -r "(keyword(bug) or keyword(issue)) and not ancestors(tagged())"