[Dependabot]: Update lxml requirement from ~=5.2 to ~=5.3

Updates the requirements on [lxml](https://github.com/lxml/lxml) to permit the latest version.
- [Release notes](https://github.com/lxml/lxml/releases)
- [Changelog](https://github.com/lxml/lxml/blob/master/CHANGES.txt)
- [Commits](lxml/lxml@lxml-5.2.0...lxml-5.3.0)

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

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

requirements.txt

@@ -1,3 +1,3 @@
 pyTooling ~= 6.4
 ruamel.yaml ~= 0.18.6
-lxml ~= 5.2
+lxml ~= 5.3

tests/requirements.txt

@@ -10,4 +10,4 @@ pytest-cov ~= 5.0
 # Static Type Checking
 mypy ~= 1.10
 typing_extensions ~= 4.12
-lxml ~= 5.2
+lxml ~= 5.3