build: Unpin lxml.

libxmlsec and lxml need to be updated in lockstep and the version we had
wouldn't work with Ubuntu 24.04 so unpinning lxml along with libxmlsec
to see if that resolves the build and dependency issues.

requirements/constraints.txt

@@ -105,13 +105,6 @@ event-tracking==3.0.0
 # https://github.com/openedx/edx-platform/issues/31616
 libsass==0.10.0
 
-# Date: 2024-04-30
-# lxml>=5.0 introduced breaking changes related to system dependencies
-# lxml==5.2.1 introduced new extra so we'll nee to rename lxml --> lxml[html-clean]
-# This constraint can be removed once we upgrade to Python 3.11
-# Issue for unpinning: https://github.com/openedx/edx-platform/issues/35272
-lxml<5.0
-
 # Date: 2018-12-14
 # markdown>=3.4.0 has failures due to internal refactorings which causes the tests to fail
 # pinning the version untill the issue gets resolved in the package itself

requirements/edx/kernel.in

@@ -103,7 +103,7 @@ importlib_metadata                  # Used to access entry_points in i18n_api pl
 jsonfield                           # Django model field for validated JSON; used in several apps
 laboratory                          # Library for testing that code refactors/infrastructure changes produce identical results
 importlib_metadata                  # Used to access entry_points in i18n_api plugin
-lxml                                # XML parser
+lxml[html_clean]                    # XML parser
 lti-consumer-xblock>=7.3.0
 mako                                # Primary template language used for server-side page rendering
 Markdown                            # Convert text markup to HTML; used in capa problems, forums, and course wikis