Revert "Update docs with new `fx run` format"

This reverts commit 2cfa603e.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> Update docs with new `fx run` format
> 
> Bug: None
> Test: None
> Change-Id: Ifb7c85b400a48fc9913c54f57a1a17f5ed87e56a

TBR=mcgrathr@google.com,porce@google.com,awolter@google.com,brettw@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: None
Change-Id: Ie07c7363006e5980685a2aa07b1231861f745094