chore(exoflex): bump release-it to v15.6

[darcien]

Why

Current release-it version in exoflex is failing when trying to release. Tried with node v12, v14, and v16.

Logs

$ yarn release-it
yarn run v1.22.18
$ /Users/darcien/projects/infra/packages/exoflex/node_modules/.bin/release-it
(node:85406) Warning: Accessing non-existent property 'cat' of module exports inside circular dependency
(Use `node --trace-warnings ...` to show where the warning was created)
(node:85406) Warning: Accessing non-existent property 'cd' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'chmod' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'cp' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'dirs' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'pushd' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'popd' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'echo' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'tempdir' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'pwd' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'exec' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'ls' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'find' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'grep' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'head' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'ln' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'mkdir' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'rm' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'mv' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'sed' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'set' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'sort' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'tail' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'test' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'to' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'toEnd' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'touch' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'uniq' of module exports inside circular dependency
(node:85406) Warning: Accessing non-existent property 'which' of module exports inside circular dependency
ERROR undefined is not iterable (cannot read property Symbol(Symbol.iterator))
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.