Make get_unchecked(_mut) docs consistent

.mailmap

@@ -491,7 +491,6 @@ Milan Landaverde <milanlandaverde@gmail.com>
 mjptree <michael.prantl@hotmail.de>
 Ms2ger <ms2ger@gmail.com> <Ms2ger@gmail.com>
 msizanoen1 <qtmlabs@protonmail.com>
-mu001999 <mu001999@outlook.com> <rcu@live.com>
 Mukilan Thiagarajan <mukilanthiagarajan@gmail.com>
 Nadrieril Feneanar <Nadrieril@users.noreply.github.com>
 Nadrieril Feneanar <Nadrieril@users.noreply.github.com> <nadrieril+rust@gmail.com>
@@ -603,6 +602,7 @@ Robert Habermeier <rphmeier@gmail.com>
 Robert Millar <robert.millar@cantab.net>
 Roc Yu <rocyu@protonmail.com>
 Rohit Joshi <rohitjoshi@users.noreply.github.com> Rohit Joshi <rohit.joshi@capitalone.com>
+Roland Xu <rcu@live.com> <mu001999@outlook.com>
 Ross Smyth <18294397+RossSmyth@users.noreply.github.com>
 Ross Smyth <18294397+RossSmyth@users.noreply.github.com> <crs2017@gmail.com>
 Ross Smyth <18294397+RossSmyth@users.noreply.github.com> <rsmyth@electrocraft.com>