updated lima config ssh forwardAgent true by default

[johnkraczek]

Fixes #402

Setting the ssh: forwardAgent: true in the lima config allows the agent to be forwarded. If you are good with that being the default then that's all that is needed.

[swalkinshaw]

I'm good with this being the default. I can't see why we'd want it be disabled but we can always make it configurable in the future 👍

@johnkraczek there's a test that needs to be updated as well: https://github.com/roots/trellis-cli/blob/4a8d8ac82bc506cd89fd659206919e202b27c6e4/pkg/lima/instance_test.go#L13-L88

The expected output needs to have the new ssh entry

[swalkinshaw]

Thank you!