The ${{\boldsymbol{\Lambda }}}_{{\boldsymbol{b}}}\, \rightarrow \,{\boldsymbol{\Lambda }}\,( \rightarrow {\boldsymbol{p}}{{\boldsymbol{\pi }}}^{-}){{\boldsymbol{\mu }}}^{+}{{\boldsymbol{\mu }}}^{-}$ decay in the ${{\rm{RS}}}_{{\boldsymbol{c}}}$ model