playTests.sh does no longer needs grep -E

it makes the test script more portable across posix systems
because `grep -E` is not guaranteed
while `grep` is fairly common.

programs/fileio_asyncio.c

@@ -453,8 +453,8 @@ static IOJob_t* AIO_ReadPool_findNextWaitingOffsetCompletedJob_locked(ReadPoolCt
 /* AIO_ReadPool_numReadsInFlight:
  * Returns the number of IO read jobs currently in flight. */
 static size_t AIO_ReadPool_numReadsInFlight(ReadPoolCtx_t* ctx) {
-    const size_t jobsHeld = (ctx->currentJobHeld==NULL ? 0 : 1);
-    return ctx->base.totalIoJobs - (ctx->base.availableJobsCount + ctx->completedJobsCount + jobsHeld);
+    const int jobsHeld = (ctx->currentJobHeld==NULL ? 0 : 1);
+    return (size_t)(ctx->base.totalIoJobs - (ctx->base.availableJobsCount + ctx->completedJobsCount + jobsHeld));
 }
 
 /* AIO_ReadPool_getNextCompletedJob: