fix: elixir 1.19 and 1.20 compiler warnings

[David-Klemenc]

Currently elixir v 1.19.5 and 1.20.0-rc.1 give warnings like:

==> exsync
Compiling 7 files (.ex)
    warning: a struct for ExSync.SrcMonitor.State is expected on struct update:

        %ExSync.SrcMonitor.State{state | throttle_timer: nil}

    but got type:

        dynamic()

    where "state" was given the type:

        # type: dynamic()
        # from: lib/exsync/src_monitor.ex:55:45
        state

    when defining the variable "state", you must also pattern match on "%ExSync.SrcMonitor.State{}".

    hint: given pattern matching is enough to catch typing errors, you may optionally convert the struct update into a map update. For example, instead of:

        user = some_function()
        %User{user | name: "John Doe"}

    it is enough to write:

        %User{} = user = some_function()
        %{user | name: "John Doe"}

    typing violation found at:
    │
 57 │     state = %State{state | throttle_timer: nil}
    │             ~
    │
    └─ lib/exsync/src_monitor.ex:57:13: ExSync.SrcMonitor.handle_info/2

P.S. noticed #63 a bit late -> can make another PR just removing:

require Logger

from application.ex ?