(REF) CRM_Utils_Hook - Remove deprecated formulations of `invoke(int,...)`

(REF) CRM_Utils_Hook - Remove deprecated formulations of `invoke(int,...)`

Overview
--------

The signature of `CRM_Utils_Hook::invoke()` originally took an argument `int
$count` (number of hook args), but circa 4.7 it changed to prefer `string[]
$names` (symbolic names for each hook arg).  The `int` notation doesn't
provide enough information to fire via Symfony EventDispatcher and was
mostly replaced/deprecated, but `int` notation is still supported for
backward compatibility.

This cleans a couple oddballs using the `int` notation.

Before
------

Some stub functions in `CRM_Utils_Hook` still use the `invoke(int,...)` formulation:

* `hook_themes` fell through a crack because it had a long PR (years?) that
   overlapped with the change in `invoke()`.
* `hook_install` (etc) looks like `int`, but it's not actually used.

After
-----

None of the stub functions in `CRM_Utils_Hook::invoke(string[], ...)` use
`int` formulation.