fix(ui): fix filter dropdown rendering behind table rows (#173)

## Summary
- Filter dropdowns on the /runs page (Suite, Strategy, etc.) were
rendering behind table rows due to insufficient z-index
- Bumped `ListboxOptions` z-index from `z-10` to `z-50`

## Test plan
- [x] On /runs, click the Suite filter dropdown — verify it renders
above the table

Author: skylenet

ui/src/components/runs/RunFilters.tsx

@@ -69,7 +69,7 @@ function FilterDropdown<T extends string>({
               <ChevronIcon />
             </span>
           </ListboxButton>
-          <ListboxOptions className="absolute z-10 mt-1 max-h-60 w-full min-w-max overflow-auto rounded-sm bg-white py-1 text-base shadow-sm ring-1 ring-black/5 focus:outline-hidden dark:bg-gray-800 dark:ring-gray-700">
+          <ListboxOptions className="absolute z-50 mt-1 max-h-60 w-full min-w-max overflow-auto rounded-sm bg-white py-1 text-base shadow-sm ring-1 ring-black/5 focus:outline-hidden dark:bg-gray-800 dark:ring-gray-700">
             {options.map((option) => (
               <ListboxOption
                 key={option.value}