[Issue #1835] Remove distinct from inner query of search (#1836)

## Summary
Fixes #1835

### Time to review: __3 mins__

## Changes proposed
Adjust the search query to not do `distinct` on the inner filter query

## Context for reviewers

This distinct originally was added as the query was setup in a much
different way. We needed to do the distinct to avoid duplicates when
doing joins, but because it is now an inner query - quite literally used
as `select ... where opportunity_id in (select distinct opportunity_id
...)` we don't need to distinct it. If the values aren't distinct, it
doesn't actually change the outer query, there will just be dupes in
that list, but that's fine and seems to be better performing.

api/src/services/opportunities_v0_1/search_opportunities.py

@@ -197,7 +197,7 @@ def search_opportunities(
     a set of opportunity IDs for the outer query to filter against. This query
     ends up looking like (varying based on exact filters):
 
-        SELECT DISTINCT
+        SELECT
             opportunity.opportunity_id
         FROM opportunity
             JOIN current_opportunity_summary ON opportunity.opportunity_id = current_opportunity_summary.opportunity_id
@@ -220,9 +220,6 @@ def search_opportunities(
         )  # Only ever return non-drafts
         # Filter anything without a current opportunity summary
         .where(Opportunity.current_opportunity_summary != None)  # noqa: E711
-        # Distinct the opportunity IDs returned so that the outer query
-        # has fewer results to query against
-        .distinct()
     )
 
     # Current + Opportunity Summary are always needed so just add them here