fix bad url in std-file-readText.dd

[timotheecour]

No description provided.

[dlang-bot]

Thanks for your pull request and interest in making D better, @timotheecour! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
Please verify that your PR follows this checklist:

• My PR is fully covered with tests (you can see the annotated coverage diff directly on GitHub with CodeCov's browser extension
• My PR is as minimal as possible (smaller, focused PRs are easier to review than big ones)
• I have provided a detailed rationale explaining my changes
• New or modified functions have Ddoc comments (with Params: and Returns:)

Please see CONTRIBUTING.md for more information.

---

If you have addressed all reviews or aren't sure how to proceed, don't hesitate to ping us with a simple comment.

Bugzilla references

Your PR doesn't reference any Bugzilla issue.

If your PR contains non-trivial changes, please reference a Bugzilla issue or create a manual changelog.

[wilzbach]

Ideally we phase out this entire HTTP/HTTPS non-sense, and just use LINK2, but Andrei has been against this in the past.

[timotheecour]

breaking down links like that is UGLY and contrary to having readable docs when they're un-rendered (eg we can't simply copy paste these links to/from a browser); and it's error prone as examplified here

[wilzbach]

See also:

#4411 (comment)
#4951 (comment)

In short:

• at least there's WEB anymore
• The Ddoc issue has been fixed, so in theory we could try this again, but I'm not sure whether it's worth the pain.

Though maybe we can can @andralex's approval this time?

[andralex]

Typing https:// is awkward and integrating it in a macro is sensible. We could and should fix matters on the ddoc side; the issue of line breakage in macros is not singular to this one. Until then please leave HTTP and HTTPS where they are. Thanks.

[wilzbach]

Merged manually due to braddr/d-tester#70