[UPDATE] Update lxml requirement from <6,>=5.3.1 to >=5.3.1,<7

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](https://github.com/lxml/lxml/compare/lxml-5.3.1...lxml-6.0.0)

---
updated-dependencies:
- dependency-name: lxml
  dependency-version: 6.0.0
  dependency-type: direct:production
...

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

core/static/core/footer.scss

@@ -2,6 +2,10 @@
 @import "devices";
 
 footer.bottom-links {
+  >section>a {
+    text-align: center;
+  }
+
   @media (max-width: $small-devices) {
     margin-top: 0.6em;
     padding: 1.25em;

pyproject.toml

@@ -78,7 +78,7 @@ tests = [
     "pytest-django<5.0.0,>=4.10.0",
     "model-bakery<2.0.0,>=1.20.4",
     "beautifulsoup4>=4.13.3,<5",
-    "lxml>=5.3.1,<6",
+    "lxml>=5.3.1,<7",
 ]
 docs = [
     "mkdocs<2.0.0,>=1.6.1",