Python documents state elsewhere that a comma is not an operator, so … (GH-98736)

…calling it an operator here is confusing. See https://docs.python.org/3/reference/lexical_analysis.html#operators and https://docs.python.org/3/faq/programming.html#id22.

Author: Gerardwx

Doc/reference/expressions.rst

@@ -154,7 +154,7 @@ tuple may or may not yield the same object).
    single: , (comma)
 
 Note that tuples are not formed by the parentheses, but rather by use of the
-comma operator.  The exception is the empty tuple, for which parentheses *are*
+comma.  The exception is the empty tuple, for which parentheses *are*
 required --- allowing unparenthesized "nothing" in expressions would cause
 ambiguities and allow common typos to pass uncaught.