[over.ics.ref] Capitalize 'Exact Match' (cplusplus#7392)

Author: lprv

source/overloading.tex

@@ -2296,7 +2296,7 @@
 \pnum
 If the user-defined conversion is specified by a
 specialization of a conversion function template,
-the second standard conversion sequence shall have exact match rank.
+the second standard conversion sequence shall have Exact Match rank.
 
 \pnum
 A conversion of an expression of class type