Set opentelemetry_ecto span kind to CLIENT (#38)

From the [semantic conventions][1]:

> Span kind: MUST always be CLIENT.

[1]: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/database.md

Co-authored-by: Bryan Naegele <bryannaegele@users.noreply.github.com>

instrumentation/opentelemetry_ecto/lib/opentelemetry_ecto.ex

@@ -97,7 +97,8 @@ defmodule OpentelemetryEcto do
     s =
       OpenTelemetry.Tracer.start_span(span_name, %{
         start_time: start_time,
-        attributes: attributes ++ base_attributes
+        attributes: attributes ++ base_attributes,
+        kind: :client
       })
 
     OpenTelemetry.Span.end_span(s)

instrumentation/opentelemetry_ecto/test/opentelemetry_ecto_test.exs

@@ -39,7 +39,8 @@ defmodule OpentelemetryEctoTest do
     assert_receive {:span,
                     span(
                       name: "opentelemetry_ecto.test_repo.query:users",
-                      attributes: list
+                      attributes: list,
+                      kind: :client
                     )}
 
     assert [