component/theia: don't set editor.multiCursorModifier

This was added in 48bcc52a (software/theia: some "better" defaults,
2019-08-30) because the default keybinding to create another cursor is
alt-click, but on ChromeOS alt-click does a right click, but:
 - not everybody use ChromeOS
 - this breaks the ctrl+click shortcut to go to definition/follow link
 - it makes SlapOS' Theia behaves differently from default Theia or vscode
 - ChromeOS users can use chrome://flags/#use-search-click-for-right-click
  (I'm using this flag and this seems perfect)

component/theia/buildout.cfg

@@ -106,7 +106,6 @@ content =
                           "**/.git/**": true,
                           "**/node_modules/**": true
                       },
-                      "editor.multiCursorModifier": "ctrlCmd",
                       "editor.tabSize": 2,
                       "plantuml.server": "https://plantuml.host.vifib.net/svg/",
                       "plantuml.render": "PlantUMLServer",