bug#71734: 30.0.50; eww interprets make errors as URLs

[Stefan Kangas]

`M-x eww` currently interprets this as a URL:

    make: *** [Makefile:240: __sub-make] Error 2

I think this is due to the below commit:

```
commit 4113ac253456027c4b54b92a617e0c2b3003a049
Author: Lars Ingebrigtsen <larsi@gnus.org>
Date:   Sun Jan 11 15:58:10 2015 +0100

    Further eww URL DWIM tweaks

    * net/eww.el (eww): Interpret anything that looks like a protocol
    designator as a full URL.

diff --git a/lisp/net/eww.el b/lisp/net/eww.el
--- a/lisp/net/eww.el
+++ b/lisp/net/eww.el
@@ -258,29 +258,31 @@
-         (if (or (string-match "\\`https?:" url)
+        ;; Anything that starts with something that vaguely looks
+        ;; like a protocol designator is interpreted as a full URL.
+         (if (or (string-match "\\`[A-Za-z]+:" url)
```

I think that this is much too dwim-y, and we should go back to the old
code.  But I have no idea why Lars made the above change in the first
place, so I'd like to check here first.  If the intention is to support
the various protocols that Emacs supports, then we should look for
exactly those and nothing else.

In GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.38, cairo version 1.16.0) of 2024-06-22 built on xxxxx
Repository revision: 014aab9847a0d3d898cb8cbc7224143f2d741abb
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12101007
System Description: Debian GNU/Linux 12 (bookworm)