fix(perf-issues): Allow http timings small drift (#54547)

### Summary
It seems there are times where the http timings are slightly off from
span duration, in the millisecond range. This is likely due to the
differences between timing the fetch operations and how
PerformanceNetworkTiming works, but for now we can ease off the exit
condition by a few milliseconds so we get subtimings when it's really
close.

Author: k-fish

static/app/components/events/interfaces/spans/utils.tsx

@@ -397,10 +397,19 @@ export function getSpanSubTimings(span: ProcessedSpanType): SubTimingInfo[] | nu
   const spanStart = subTimingMarkToTime(span, SpanSubTimingMark.SPAN_START);
   const spanEnd = subTimingMarkToTime(span, SpanSubTimingMark.SPAN_END);
 
+  const TEN_MS = 0.001;
+
   for (const def of timingDefinitions) {
     const start = subTimingMarkToTime(span, def.startMark);
     const end = subTimingMarkToTime(span, def.endMark);
-    if (!start || !end || !spanStart || !spanEnd || start < spanStart || end > spanEnd) {
+    if (
+      !start ||
+      !end ||
+      !spanStart ||
+      !spanEnd ||
+      start < spanStart - TEN_MS ||
+      end > spanEnd + TEN_MS
+    ) {
       return null;
     }
     timings.push({