Fixup action name for the GH marketplace

We seemed to have published to the marketplace previously with
a description of the action vs the action name. This commit changes the name
to simply `setup-beam`.

action.yml

@@ -1,5 +1,5 @@
 ---
-name: Setup Erlang/OTP with optional Elixir (and mix) and/or rebar3
+name: setup-beam
 description: >
   Set up a specific version of Erlang/OTP, Elixir, and/or rebar3
   and add the command-line tools to the PATH