Use Oxford comma

Author: hewillk

source/containers.tex

@@ -13144,7 +13144,7 @@
 The exposition-only alias template \exposid{iter-value-type}
 defined in \ref{sequences.general} and
 the exposition-only alias templates \exposid{iter-key-type}, \exposid{iter-mapped-type},
-\exposid{range-key-type} and \exposid{range-mapped-type}
+\exposid{range-key-type}, and \exposid{range-mapped-type}
 defined in \ref{associative.general}
 may appear in deduction guides for container adaptors.