Use sentence case in section titles consistently

abalkin · abalkin · commit 50ba19ee454e · 2010-12-15T19:47:37.000Z
diff --git a/Doc/reference/expressions.rst b/Doc/reference/expressions.rst
@@ -1161,7 +1161,7 @@ not bother to return a value of the same type as its argument, so e.g., ``not
 'foo'`` yields ``False``, not ``''``.)
 
 
-Conditional Expressions
+Conditional expressions
 =======================
 
 .. index::
