Revert "temporary patch to work around a problem with BSD/ocamltest/fork"

This reverts commit 309bad6197.

The problem that made this commit necessary has since bben fixed, in
commit 6015d60fc6.

tools/ci/inria/main

@@ -96,12 +96,6 @@ case "${OCAML_ARCH}" in
   bsd|macos|linux) renice 10 $$ ;;
 esac
 
-# work around a bug (in ocamltest maybe? -- to be investigated) that leaves
-# some processes running in an infinite loop after the tests are done
-case "${OCAML_ARCH}" in
-  bsd) ulimit -t 1800 ;;
-esac
-
 # be verbose and stop on error
 set -ex