tests: fix desc for "can add shims to PATH more than once"

This seems to have not been merged properly.

A similar issue is with the test for fish, which has been submitted as a
PR for rbenv: https://github.com/sstephenson/rbenv/pull/722.

test/init.bats

@@ -64,7 +64,7 @@ load test_helper
   assert_line 0 "setenv PATH '${PYENV_ROOT}/shims' \$PATH"
 }
 
-@test "doesn't add shims to PATH more than once" {
+@test "can add shims to PATH more than once" {
   export PATH="${PYENV_ROOT}/shims:$PATH"
   run pyenv-init - bash
   assert_success