Remove mentions of "since OTP27+"

Author: sabiwara

lib/elixir/pages/getting-started/debugging.md

@@ -160,8 +160,6 @@ iex> :observer.start()
 > When running `iex` inside a project with `iex -S mix`, `observer` won't be available as a dependency. To do so, you will need to call the following functions before:
 >
 > ```elixir
-> iex> Mix.ensure_application!(:wx)             # Not necessary on Erlang/OTP 27+
-> iex> Mix.ensure_application!(:runtime_tools)  # Not necessary on Erlang/OTP 27+
 > iex> Mix.ensure_application!(:observer)
 > iex> :observer.start()
 > ```

lib/elixir/src/elixir_expand.erl

@@ -1128,7 +1128,7 @@ assert_no_underscore_clause_in_cond(_Other, _E) ->
 %% Errors
 
 format_error(invalid_match_on_zero_float) ->
-  "pattern matching on 0.0 is equivalent to matching only on +0.0 from Erlang/OTP 27+. Instead you must match on +0.0 or -0.0";
+  "pattern matching on 0.0 is equivalent to matching only on +0.0. Instead you must match on +0.0 or -0.0";
 format_error({useless_literal, Term}) ->
   io_lib:format("code block contains unused literal ~ts "
                 "(remove the literal or assign it to _ to avoid warnings)",