Update CONTRIBUTING.md for revised GitHub workflows

Author: mpilgrem

CONTRIBUTING.md

@@ -349,7 +349,8 @@ This workflow will run if:
 * any tag is created
 * requested
 
-The workflow has two jobs: `integration-tests` and `github-release`.
+The workflow has three jobs: `integration-tests`, `linux-arm64` and
+`github-release`.
 
 The `integration-tests` job runs on a matrix of operating systems (`ubuntu`,
 `windows` and `macos`) and makes use of the `release.hs` script at
@@ -363,36 +364,27 @@ Its 'Build bindist' step uses `release.hs build`.
 Its 'Upload bindist' step uploads artifacts using the name of the runner's
 operating system (`Linux`, `Windows` or `macOS`) as the name for the artifacts.
 
-The `github-release` job needs `integration-tests` and only takes effect if the
-trigger for the workflow was the creation of a tag.
+The `linux-arm64` job runs on a self-hosted runner for Linux and ARM64. It makes
+use of Docker and a Docker file at `etc/dockerfiles/arm64.Dockerfile`.
 
-Its steps `Download Linux/Windows/macOS artifact` download the named artifacts
-to path `_release`.
+Its 'Build bindist' step makes use of a compiled version of `release.hs` script
+at `etc/scripts` to command `release build`.
+
+Its 'Upload bindist' step uploads artifacts using `Linux-ARM64` as the name for
+the artifacts.
+
+The `github-release` job needs `integration-tests` and `linux-arm64`. It only
+takes effect if the trigger for the workflow was the creation of a tag.
+
+Its four steps `Download Linux/Windows/macOS/Linux-ARM64 artifact` download the
+named artifacts to path `_release`.
 
 Its step 'Hash and sign assets' makes use of a 'secret' environment variable
 `RELEASE_SIGNING_KEY` established by the owner of the Stack repository. The
 variable contains the private key for the GPG key with ID 0x575159689BEFB442.
 That key is imported into GPG and then used by GPG to create a detached signture
 for each file.
 
-### ARM64 (AArch64) release - `arm64-release.yml`
-
-This workflow will run if:
-* there is a pull request
-* commits are pushed to these branches: `master`, `stable` and `rc/**`
-* any tag is created
-* requested
-
-The workflow has one job (`arm64`). It runs on a self-hosted runner for Linux
-and ARM64. It makes use of Docker and a Docker file at
-`etc/dockerfiles/arm64.Dockerfile`.
-
-Its 'Build bindist' step makes use of a compiled version of `release.hs` script
-at `etc/scripts` to command `release build`.
-
-Its 'Upload bindist' step uploads artifacts using `Linux-ARM64` as the name for
-the artifacts.
-
 ### Inactive - `stan.yml`
 
 Stan is a Haskell static analysis tool. As of 29 August 2022, it does not