Minor UX issues in Filter Streams sessions

**Describe the bug (required)** A clear and concise description of what the bug
is.

There are two minor UX issues in Filter Streams sessions. Some content from the table below is visible in the popup.

**Expected behavior (required)** A clear and concise description of what you
expected to happen.
The popup should not show anything from the content below.

**To Reproduce (required)** Steps to reproduce the behavior:
- Stream page > Sessions section > Filter > Popup shows content from the content below
- Stream Sessions list page > Filter > Popup shows content from the content below

**Device (required):**
Any.

**Screenshots (optional)** If applicable, add screenshots to help explain your
problem.

**Additional context (optional)** Add any other context about the problem here.
The popup is implemented with DropdownMenu component.
The DropdownMenuContentWrapper has `z-index: auto`. Setting it to `1` already solves the problem. But this is probably not the right fix.