[librsvg: 4/5] CONTRIBUTING.md: no need to recommend rust nightly anymore

[Federico Mena Quintero <federico src gnome org>]

commit 4f45f2ced60dbd4328725b83d4357b3ed89866ba
Author: Federico Mena Quintero <federico gnome org>
Date:   Fri Jun 18 10:02:24 2021 -0500

    CONTRIBUTING.md: no need to recommend rust nightly anymore
    
    Also, rsvg-view-3 doesn't exist anymore!
    
    Part-of: <https://gitlab.gnome.org/GNOME/librsvg/-/merge_requests/551>

 CONTRIBUTING.md | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)
---
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 52e28948..cc9018f6 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -167,14 +167,6 @@ of CI pipelines will fail:
     indentation, but don't want it to make changes on its own:  
     `cargo fmt --all -- --check`
 
-***Installing rustfmt*** As of 2018/Sep, our continuous integration
-pipeline assumes the version of rustfmt that is distributed through the
-nightly channel of [rustup](rustup.rs).  You can install it with
-
-```
-rustup component add rustfmt-preview --toolchain=nightly
-```
-
 ### Test suite
 
 Please make sure that the test suite passes with the changes in your
@@ -201,11 +193,11 @@ librsvg, and run this:
 
 ```
 cd /src/librsvg
-libtool --mode=execute ./rsvg-convert -o foo.png foo.svg
+cargo build
+./target/debug/rsvg-convert -o foo.png foo.svg
 ```
 
-Then you can view the resulting `foo.png` image.  Alternatively, you
-can use `./rsvg-view-3` for a quick-and-dirty SVG viewer.
+Then you can view the resulting `foo.png` image.
 
 **Please update the test suite** with a suitable example file once you
 have things working (or before even writing code, if you like