update the guide to reflect the new version number, and that libjemalloc is no longer required

Author: tayloraswift

Guides/docs.docc/Quickstart.md

@@ -1,6 +1,6 @@
 # Previewing documentation locally
 
-This guide walks through how to use the `unidoc preview` tool to preview documentation locally on macOS 14. This guide won’t make any effort to explain how Unidoc itself works, it is merely intended to demonstrate how to preview multi-package documentation as quickly as possible. For a more-detailed Linux-centric tour, see the <doc:Getting-started> guide.
+This guide walks through how to use the `unidoc preview` tool to preview documentation locally on macOS 15. This guide won’t make any effort to explain how Unidoc itself works, it is merely intended to demonstrate how to preview multi-package documentation as quickly as possible. For a more-detailed Linux-centric tour, see the <doc:Getting-started> guide.
 
 In this guide, you will:
 
@@ -37,10 +37,6 @@ You can download and install the binary under `/usr/local/bin` like this:
 
 @Code(file: unidoc-install.sh, title: unidoc-install.sh)
 
->   Important:
->   On Linux, the prebuilt binaries use [jemalloc](https://jemalloc.net/) instead of the default
->   system allocator. You can install it on Ubuntu with `sudo apt install libjemalloc2`.
-
 ### Building Unidoc from source
 
 Unidoc is an ordinary SwiftPM executable product. You can build it for your macOS host like this:

Guides/docs.docc/local/unidoc-install.sh

@@ -1,5 +1,5 @@
 UNIDOC_MIRROR=https://static.swiftinit.org/unidoc
-UNIDOC_VERSION=0.19.6
+UNIDOC_VERSION=0.20.0
 UNIDOC_PLATFORM=macOS-ARM64
 
 curl -L $UNIDOC_MIRROR/$UNIDOC_VERSION/$UNIDOC_PLATFORM/unidoc.tar.gz \