Hello Hisham
You’ll notice that ports G0/1 and G0/2 on SW2 have no switchport mode configuration. This means that by default, they are indeed in access mode. But remember that Dynamic Trunking Protocol (DTP) is enabled by default on both switches as well. This means that if you configure the SW1 port-channel as a trunk (which in turn configures the physical ports as trunks), DTP packets will be sent to SW2. When SW2 receives DTP packets that request to form a trunk, the SW2 interfaces will change to trunk mode.
More about DTP (and how to disable it) can be found in the following lesson:
I hope this has been helpful!
Laz