chore: update test name and add comment

libs/positions/src/lib/positions-manager.spec.tsx

@@ -31,7 +31,7 @@ jest.mock('@vegaprotocol/data-provider', () => ({
 }));
 
 describe('PositionsManager', () => {
-  it('should close position with max uint64', async () => {
+  it('should close position with half of max uint64', async () => {
     render(<PositionsManager partyIds={['partyId']} isReadOnly={false} />, {
       wrapper: MockedProvider,
     });

libs/utils/src/lib/constants.ts

@@ -1,2 +1,3 @@
 export const MAXGOINT64 = '9223372036854775807';
+// The fix for the close position functionality needs MaxInt64/2 for the size
 export const HALFMAXGOINT64 = '4611686018427387903';