[expr.ass] Replace text \term with code \placeholder for "op="

Author: tkoeppe

source/expressions.tex

@@ -4828,8 +4828,8 @@
 \impldefplain{value of bit-field that cannot represent!assigned value}.
 
 \pnum
-The behavior of an expression of the form \tcode{E1} \term{op}\tcode{=}
-\tcode{E2} is equivalent to \tcode{E1 = E1} \term{op} \tcode{E2} except
+The behavior of an expression of the form \tcode{E1 \placeholder{op}= E2}
+is equivalent to \tcode{E1 = E1 \placeholder{op} E2} except
 that \tcode{E1} is evaluated only once. In \tcode{+=} and \tcode{-=},
 \tcode{E1} shall either have arithmetic type or be a pointer to a
 possibly cv-qualified completely-defined object type. In all other