docs: update Dockerfile

docs: update Dockerfile

Fix issues in Dockerfile:
1. Update Fedora image to the latest version 41, otherwise docker build
   fails with an error:

   Step 1/7 : FROM registry.fedoraproject.org/fedora:28
   manifest for registry.fedoraproject.org/fedora:28 not found: manifest unknown: manifest unknown

2. Force install python3-yaml package, as it's required for running some
   tests. For example, tests/test-remote-headers.sh will fail without
   it:

   V=$($CMD_PREFIX ostree --version | \
       python3 -c 'import sys, yaml; print(yaml.safe_load(sys.stdin)["libostree"]["Version"])')
   Traceback (most recent call last):
   File "<string>", line 1, in <module>
    import sys, yaml; print(yaml.safe_load(sys.stdin)["libostree"]["Version"])
    ^^^^^^^^^^^^^^^^
   ModuleNotFoundError: No module named 'yaml'

With these fixes `make check` executes successfully in a container:
============================================================================
Testsuite summary for libostree 2024.11
============================================================================
 TOTAL: 935
 PASS:  888
 SKIP:  47
 XFAIL: 0
 FAIL:  0
 XPASS: 0
 ERROR: 0

Signed-off-by: Igor Opaniuk <igor.opaniuk@foundries.io>