Fix #631, Remove README link to empty fs_lib repository

[thnkslprpt]

Checklist

• I reviewed the Contributing Guide.
• I signed and emailed the appropriate Contributor License Agreement to GSFC-SoftwareRelease@mail.nasa.gov and copied cfs-program@lists.nasa.gov.

Describe the contribution
Fixes #631
Removes link to empty fs_lib repository

Expected behavior changes
None

Contributor Info
Avi Weiss @thnkslprpt

[skliper]

Historically I used this list to keep track of the open source repos out there, but maybe that's not necessary anymore. Up to @dmknutsen, but maybe just add a note it's not populated yet or planned future work or similar? I think there are a few others that are empty/stale/dormant.