[Spec change] Fix description of sycl::free

[sycl-issue-bot]

Please review whether KhronosGroup/SYCL-Docs#758 by @Pennycook requires any changes to the CTS.

If changes are required: Open a new PR addressing the changes and link it to this issue.
If no changes are required: Close this issue and proceed with the spec PR.

[Pennycook]

I don't think this is an easy one to answer, because there may be CTS tests that rely on specific behaviors of sycl::free.

My recommendation would be to close this issue because no CTS test changes are required now, but with the expectation that we may need to adjust some tests later if an implementation fails a test due to the test making an invalid assumption. The alternative would be to review every CTS test to ensure that every usage of sycl::free is safe, which is a non-trivial amount of work.