[Fleet] Fix flaky jest tests (#190778)

Fixes https://github.com/elastic/kibana/issues/189868
Fixes https://github.com/elastic/kibana/issues/189869

## Summary
Fix flaky unit tests. Tested locally and on ci, note that flaky test
runner cannot be used with jest tests.


### Checklist

- [ ] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/create_package_policy_page/components/steps/step_select_agent_policy.test.tsx

@@ -83,6 +83,8 @@ describe('step select agent policy', () => {
   beforeEach(() => {
     testRenderer = createFleetTestRendererMock();
     useMultipleAgentPoliciesMock.mockReturnValue({ canUseMultipleAgentPolicies: false });
+  });
+  afterEach(() => {
     updateAgentPoliciesMock.mockReset();
   });
 
@@ -110,7 +112,7 @@ describe('step select agent policy', () => {
   });
 
   test('should select agent policy by default if one exists', async () => {
-    useGetAgentPoliciesMock.mockReturnValueOnce({
+    useGetAgentPoliciesMock.mockReturnValue({
       data: { items: [{ id: 'policy-1', name: 'Policy 1' }] },
       error: undefined,
       isLoading: false,