*: make TestLogicalOverflow stable (#8075)

close #7017

Signed-off-by: Ryan Leung <[email protected]>

tests/server/tso/global_tso_test.go

@@ -165,7 +165,7 @@ func TestLogicalOverflow(t *testing.T) {
 			re.NoError(err)
 			if i == 1 {
 				// the 2nd request may (but not must) overflow, as max logical interval is 262144
-				re.Less(time.Since(begin), updateInterval+20*time.Millisecond) // additional 20ms for gRPC latency
+				re.Less(time.Since(begin), updateInterval+50*time.Millisecond) // additional 50ms for gRPC latency
 			}
 		}
 		// the 3rd request must overflow