address github comments

Author: Qinghao Shi

APIs_Drivers/QSPI/main.cpp

@@ -53,7 +53,7 @@ static bool mem_ready()
         if (QSPI_STATUS_OK != qspi_device.command_transfer(CMD_RDSR, -1, NULL, 0, status_value, STATUS_REG_SIZE)) {
             printf("Reading Status Register failed \n");
         }
-        wait_us(1000);
+        ThisThread::sleep_for(1);
     } while ((status_value[0] & BIT_WIP) != 0 && retries);
 
     if ((status_value[0] & BIT_WIP) != 0) {

Tutorials_UsingAPIs/Flow-Control-Interrupt-Button/main.cpp

@@ -14,6 +14,6 @@ int main()
     button.rise(&toggle);  // call toggle function on the rising edge
     while (1) {            // wait around, interrupts will interrupt this!
         heartbeat = !heartbeat;
-        wait_us(250000);
+        ThisThread::sleep_for(250);
     }
 }

Tutorials_UsingAPIs/Flow-Control-Ticker/main.cpp

@@ -17,6 +17,6 @@ int main()
     // spin in a main loop. flipper will interrupt it to call flip
     while (1) {
         led1 = !led1;
-        wait_us(200000);
+        ThisThread::sleep_for((200);
     }
 }