Update installation instructions

INSTALLATION.md

@@ -43,8 +43,7 @@ brew install mysql bison openssl mysql-client
 bundle config --global build.mysql2 --with-opt-dir="$(brew --prefix openssl)"
 ```
 
-QPixel development requires Ruby 2.7+.
-For a production instance, Ruby 2.6+ is required (but 2.7+ is recommended).
+QPixel requires Ruby 2.7+.
 
 ### Install JS runtime
 
@@ -57,15 +56,13 @@ If you already have Node.JS installed, you can skip this step. If not,
 If you haven't already got it, [download and install Redis](https://redis.io/download)
 or for example `sudo apt install redis-server`.
 
-### Install Imagemagick
+### Install Libvips
 
-If you haven't already installed Imagemagick, you'll need to [install it for
-your system](https://imagemagick.org/script/download.php).
+If you haven't already installed Libvips, you'll need to [install it for
+your system](https://www.libvips.org/).
 
-If you install Imagemagick from APT on a Debian-based system, you may need to
-also install the `libmagickwand-dev` package.
-
-`sudo apt install libmagick++-dev` should also work.
+To install libvips from APT on a Debian-based system, use
+`sudo apt install libvips`
 
 ## Install QPixel