fix comma location in various places (GH-19233)

diff --git a/Doc/reference/expressions.rst b/Doc/reference/expressions.rst
index 3fcc5e1..16542cd 100644
--- a/Doc/reference/expressions.rst
+++ b/Doc/reference/expressions.rst
@@ -28,7 +28,7 @@
 .. index:: pair: arithmetic; conversion
 
 When a description of an arithmetic operator below uses the phrase "the numeric
-arguments are converted to a common type," this means that the operator
+arguments are converted to a common type", this means that the operator
 implementation for built-in types works as follows:
 
 * If either argument is a complex number, the other is converted to complex;