internal/wire: use full go run command in go:generate comment

[steebchen]

Change the go:generate command to use the full go run ... command
to ensure the version specified in the current go module is used
instead of the global binary.

fix #160

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[steebchen]

@googlebot I signed it!

[zombiezen]

Sorry for the delay. This is still on my radar to review, but I've been swamped with other life commitments. I will try to get to this sometime over the next few weeks.

[steebchen]

Sure, no worries

[zombiezen]

LGTM. Thanks for your patience!