Description of problem:

No `deprecatetruncate` sub-command:
mac:operator-registry jianzhang$ ./bin/opm index --help
generate operator index container images from preexisting operator bundles

Usage:
  opm index [command]

Available Commands:
  add               Add operator bundles to an index.
  export            Export an operator from an index into the appregistry format
  prune             prune an index of all but specified packages
  prune-stranded    prune an index of stranded bundles
  rm                delete an entire operator from an index

Flags:
  -h, --help   help for index

Global Flags:
      --skip-tls   skip TLS certificate verification for container image registries while pulling bundles or index

Version-Release number of selected component (if applicable):
mac:operator-registry jianzhang$ ./bin/opm  version
Version: version.Version{OpmVersion:"v1.6.1-249-gcde92c13", GitCommit:"cde92c13", BuildDate:"2020-08-31T02:14:12Z", GoOs:"darwin", GoArch:"amd64"}

How reproducible:
always

Steps to Reproduce:
1. Install the `opm` binary.
2. Check the output of the `opm index`
3.

Actual results:
No `deprecatetruncate` sub-command.

Expected results:
Should display it.

Additional info: