component/theia: remove buggy `which` command

This does not work as expected with in this situation :

   bash-5.1$ which slapos
   /usr/bin/slapos
   bash-5.1$ /usr/bin/which slapos
   /opt/slapgrid/d4af5a4bc0958cc5f60fac0dbf6c916e/bin/slapos
   bash-5.1$ ls -al /opt/slapgrid/d4af5a4bc0958cc5f60fac0dbf6c916e/bin/slapos
   -rwxr-x--- 1 slapsoft slapsoft 3492 Jan 31 10:01 /opt/slapgrid/d4af5a4bc0958cc5f60fac0dbf6c916e/bin/slapos
   bash-5.1$ id
   uid=957(slapuser39) gid=1041(slapuser39) groups=1041(slapuser39),1001(slapsoft)

component/theia/buildout.cfg

@@ -70,6 +70,10 @@ post-install =
   # and anyway not used once the software is installed
   rm -f %(location)s/node_modules/@msgpackr-extract/*/*.node
   rm -rf $HOME/.cache/yarn/
+  # remove "which" command added in $PATH that does not correctly
+  # handle executables thanks to a secondary group of the user.
+  # https://www.npmjs.com/package/which https://www.npmjs.com/package/isexe
+  rm -f %(location)s/node_modules/.bin/which
 
 [theia-wrapper]
 recipe = slapos.recipe.template