Remove custom elixir_ls installation

I switched to using the native neovim LSP integration, and
`nvim-lspconfig` is significantly better maintained than the various
`coc-*` packages, so we no longer need this.

roles/development_workstation/tasks/neovim.yml

@@ -25,23 +25,3 @@
     creates: "{{ home }}/.local/bin/nvim"
   tags:
     - neovim
-
-- name: Install the Elixir language server manually
-  tags:
-    - neovim
-    - lsp
-  block:
-    - name: Clone elixir-ls
-      ansible.builtin.git:
-        repo: https://github.com/elixir-lsp/elixir-ls.git
-        dest: "{{ third_party_src }}/elixir-ls"
-        update: true
-        force: true
-
-    # We won't have elixir installed yet, so we just dump the commands into a
-    # script to at least make it easier for manual execution later.
-    - name: Add build script
-      ansible.builtin.copy:
-        content: "mix deps.get && mix compile && mix elixir_ls.release -o release"
-        dest: "{{ third_party_src }}/elixir-ls/build.sh"
-        mode: "0755"