[dev-context] Typo in mp-tool

--- /opt/luametatex/texmf-context/metapost/context/base/mpiv/mp-tool.mpiv 2020-01-01 13:22:40.000000000 -0500 +++ mp-tool.mpiv 2020-02-28 22:24:09.527072792 -0500 @@ -641,7 +641,7 @@ addto currentpicture also pattern ; addto currentpicture also shape ; fi ; - currentpicture := currentpicture shifted - centrum ; + currentpicture := currentpicture shifted centrum ; endgroup ; ) enddef;