fix(backport): Use 'paths(scalars)' as 'leaf_paths' filter is deprecated

[matthewfeickert]

• The 'leaf_paths' filter has been deprecated for 9 years and was removed in jqlang v1.7 (jq v1.6) so use the 'paths(scalars)' filter.

  • c.f. Remove deprecated filters: leaf_paths, recurse_down jqlang/jq#2666
  • c.f. Simplified standard library; marked redundant filters as duplicated jqlang/jq#426

• Remove upper bound on jq version

  • Reverts build: Restrict jq to jqlang pre v1.7 #97

• Backport PR fix: Use 'paths(scalars)' as 'leaf_paths' filter is deprecated  #99

* Backport PR https://github.com/yadage/packtivity/pull/99
* The 'leaf_paths' filter has been deprecated for 9 years and was removed in jqlang v1.7 (jq v1.6) so use the 'paths(scalars)' filter.
   - c.f. https://github.com/jqlang/jq/pull/2666
   - c.f. https://github.com/jqlang/jq/pull/426
* Remove upper bound on jq version
   - Reverts https://github.com/yadage/packtivity/pull/97