bpo-33852: Remove misplaced parentheses around 'list'. (GH-7672)

'expresson list' refers to the grammar term 'expression_list' in the subscription production.
diff --git a/Doc/reference/expressions.rst b/Doc/reference/expressions.rst
index 222b897..61bc912 100644
--- a/Doc/reference/expressions.rst
+++ b/Doc/reference/expressions.rst
@@ -772,7 +772,7 @@
 value in the mapping that corresponds to that key.  (The expression list is a
 tuple except if it has exactly one item.)
 
-If the primary is a sequence, the expression (list) must evaluate to an integer
+If the primary is a sequence, the expression list must evaluate to an integer
 or a slice (as discussed in the following section).
 
 The formal syntax makes no special provision for negative indices in