Fix bare URL with formatting

What does this merge request do and why?

This tiny MR fixes the following linting error by formatting the bare URL:

$ make lint
Vale: ✔ 0 errors, 0 warnings and 0 suggestions in 82 files.
MarkdownLint: markdownlint-cli2-config v0.6.0 (markdownlint v0.27.0)
Finding: doc/**/*.md README.md
Linting: 79 file(s)
Summary: 1 error(s)
doc/howto/saml.md:61:67 MD034/no-bare-urls Bare URL used [Context: "https://<gitlab-host>:<gitlab-..."]
make: *** [markdownlint] Error 1

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.

Closes #1660 (closed)