[8.12] [Fleet] Fix max agent for agent activity (#176081) (#176092)

# Backport

This will backport the following commits from `main` to `8.12`:
- [[Fleet] Fix max agent for agent activity
(#176081)](#176081)

<!--- Backport version: 9.4.3 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

<!--BACKPORT [{"author":{"name":"Nicolas
Chaulet","email":"[email protected]"},"sourceCommit":{"committedDate":"2024-02-01T18:59:34Z","message":"[Fleet]
Fix max agent for agent activity
(#176081)","sha":"9872b70a84f61d75243064e81abea42afdf9a58f","branchLabelMapping":{"^v8.13.0$":"main","^v(\\d+).(\\d+).\\d+$":"$1.$2"}},"sourcePullRequest":{"labels":["bug","release_note:skip","Team:Fleet","backport:prev-minor","v8.13.0"],"title":"[Fleet]
Fix max agent for agent
activity","number":176081,"url":"https://github.com/elastic/kibana/pull/176081","mergeCommit":{"message":"[Fleet]
Fix max agent for agent activity
(#176081)","sha":"9872b70a84f61d75243064e81abea42afdf9a58f"}},"sourceBranch":"main","suggestedTargetBranches":[],"targetPullRequestStates":[{"branch":"main","label":"v8.13.0","branchLabelMappingKey":"^v8.13.0$","isSourceBranch":true,"state":"MERGED","url":"https://github.com/elastic/kibana/pull/176081","number":176081,"mergeCommit":{"message":"[Fleet]
Fix max agent for agent activity
(#176081)","sha":"9872b70a84f61d75243064e81abea42afdf9a58f"}}]}]
BACKPORT-->

Co-authored-by: Nicolas Chaulet <[email protected]>

x-pack/plugins/fleet/public/applications/fleet/sections/agents/agent_list_page/components/agent_activity_flyout.tsx

@@ -58,7 +58,7 @@ const FlyoutFooterWPadding = styled(EuiFlyoutFooter)`
   padding: 16px 24px !important;
 `;
 
-const MAX_VIEW_AGENTS_COUNT = 2000;
+const MAX_VIEW_AGENTS_COUNT = 1000;
 
 export const AgentActivityFlyout: React.FunctionComponent<{
   onClose: () => void;