[set.overview] Fix punctuation (#7808)

Author: Andreas-Krug

source/containers.tex

@@ -12651,7 +12651,7 @@
 A \tcode{set} meets all of the requirements
 of a container\iref{container.reqmts},
 of a reversible container\iref{container.rev.reqmts},
-of an allocator-aware container\iref{container.alloc.reqmts}. and
+of an allocator-aware container\iref{container.alloc.reqmts}, and
 of an associative container\iref{associative.reqmts}.
 A
 \tcode{set}