docs: use proper rst markup for preformatted blocks
The multiple lines were re-flowed to a single line, both in man page and html.
--- a/mercurial/helptext/rust.txt Wed May 04 15:49:20 2022 +0200
+++ b/mercurial/helptext/rust.txt Tue May 03 12:41:21 2022 +0200
@@ -28,7 +28,8 @@
Checking for Rust
=================
-You may already have the Rust extensions depending on how you install Mercurial.
+You may already have the Rust extensions depending on how you install
+Mercurial::
$ hg debuginstall | grep -i rust
checking Rust extensions (installed)
@@ -46,7 +47,7 @@
Using pip
---------
-Users of `pip` can install the Rust extensions with the following command:
+Users of `pip` can install the Rust extensions with the following command::
$ pip install mercurial --global-option --rust --no-use-pep517