[sequence.reqmts] Fix application of P2846R6 for append_range

Author: frederick-vs-ja

source/containers.tex

@@ -1460,7 +1460,7 @@
 \recommended
 If \tcode{R} models \tcode{ranges::\libconcept{approximately_sized_range}} and
 \tcode{ranges::distance(\linebreak{}rg) <= ranges::reserve_hint(rg)} is \tcode{true},
-an implementation should not perform any reallocation.
+an implementation should not perform more than a single reallocation.
 
 \pnum
 \ensures