Remove inputUnit parameter of formatDuration

The inputUnit parameter was not used anywhere and significantly
complicated the implementation of the formatDuration function.
Now, all inputs are assumed to be in microseconds which is consistent
with a few other methods in the date.tsx file.

Signed-off-by: James Ferguson <[email protected]>

packages/jaeger-ui/src/utils/date.tsx

@@ -102,7 +102,7 @@ export function formatSecondTime(duration: number) {
  * 5000ms => 5s
  * 1000μs => 1ms
  */
-export function formatDuration(duration: number, inputUnit: string = 'microseconds'): string {
+export function formatDuration(duration: number): string {
   if (duration < 1) {
     return `${_round(duration, 2)}μs`;
   }