help: use single quotes in ``template example``

It was hard to read because ``""`` was rendered as """".

mercurial/help/templates.txt

@@ -74,9 +74,9 b" or a raw string prefix, ``r'...'``."
 
 The dot operator can be used as a shorthand for accessing a sub item:
 
-- ``expr.member`` is roughly equivalent to ``expr % "{member}"`` if ``expr``
+- ``expr.member`` is roughly equivalent to ``expr % '{member}'`` if ``expr``
   returns a non-list/dict. The returned value is not stringified.
-- ``dict.key`` is identical to ``get(dict, "key")``.
+- ``dict.key`` is identical to ``get(dict, 'key')``.
 
 Aliases
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