sg test -help doesn't print any test suites

Created by: varungandhi-src

• Commit: main @ 932da0b0fa0c7dd808951025fa409f6c848e3ee6
• Platform: macOS 12.0 on M1 MacBook Pro.

Steps to reproduce:

Run sg test -help in the sourcegraph root directory, or in some subdirectory.

Expected behavior:

It should print available test suites as written in the sg docs.

Actual behavior:

It prints the following text.

USAGE
  sg test <testsuite>

Run the given test suite.