ref(tracemetrics): Remove last function (#102817)

### Summary

In the FE list there but not supported.

Author: k-fish

static/app/views/explore/metrics/constants.tsx

@@ -154,10 +154,6 @@ export const OPTIONS_BY_TYPE: Record<string, Array<SelectOption<string>>> = {
       label: 'avg',
       value: 'avg',
     },
-    {
-      label: 'last',
-      value: 'last',
-    },
     {
       label: 'per_second',
       value: 'per_second',