refactor: remove unnecessary assertion

Author: noritaka1166

src/android.ts

@@ -19,7 +19,7 @@ export async function androidPortForward(
    systemPort: number,
    devicePort: number,
 ) {
-   await adb.forwardPort(systemPort!, devicePort);
+   await adb.forwardPort(systemPort, devicePort);
 }
 
 export async function androidRemovePortForward(adb: ADB, systemPort: number) {

src/utils.ts

@@ -161,13 +161,13 @@ export async function fetchFlutterServerPort(
             `Checking if flutter server is running on port ${systemPort || devicePort} for simulator with id ${udid}`,
          );
          await waitForFlutterServer.bind(this)(
-            (systemPort || devicePort)!,
+            (systemPort || devicePort),
             packageName,
          );
          this.log.info(
             `Flutter server is successfully running on port ${systemPort || devicePort}`,
          );
-         return (systemPort || devicePort)!;
+         return (systemPort || devicePort);
       } catch (e) {
          return null;
       }