[lib] Add "Legacy" to types in update-relationship

Summary: Based on the following commits from hackathon branch: https://github.com/CommE2E/comm/commit/9632b8c4641cfe3d1724a94da56ffdcfc226d647#diff-f60296b8773612dd2bd84b6b259c08df2ef75250493fadc5d745aa5de47b3180, https://github.com/CommE2E/comm/commit/42f28702abce0769aa1aac0417c5006faebce254

Test Plan:
Used IDE Refactor -> Rename feature.

Flow/ESLint/etc.

Reviewers: varun, tomek, ginsu, will

Reviewed By: ginsu

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D11436