Update pint requirement from >=0.17,<0.19 to >=0.17,<0.22

Updates the requirements on [pint](https://github.com/hgrecco/pint) to permit the latest version.
- [Release notes](https://github.com/hgrecco/pint/releases)
- [Changelog](https://github.com/hgrecco/pint/blob/master/CHANGES)
- [Commits](hgrecco/pint@0.17...0.21)

---
updated-dependencies:
- dependency-name: pint
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

pyproject.toml

@@ -23,7 +23,7 @@ packages = [ { include = "easyCore" } ]
 [tool.poetry.dependencies]
 python = ">=3.8"
 numpy = "^1.21"
-pint = ">=0.17,<0.19"
+pint = ">=0.17,<0.22"
 uncertainties = "^3.1"
 lmfit = "^1.0"
 bumps = ">=0.8,<0.10"