Adjust estdlib tests for stm32

Adds the stm32 platform to those that skip network tests when running the estdlib test suite.

Signed-off-by: Winford <winford@object.stream>

Author: UncleGrumpy

tests/libs/estdlib/tests.erl

@@ -31,6 +31,8 @@ start() ->
                 case atomvm:platform() of
                     emscripten ->
                         false;
+                    stm32 ->
+                        false;
                     _ ->
                         true
                 end;