Update aws-opentelemetry-distro version in Dockerfile (#346)

https://amzn-aws.slack.com/archives/C096HJWG1T6/p1763181727823969

Customers are seeing 405 errors with https://pypi.org/project/aws-opentelemetry-distro/0.13.0/

Signed-off-by: Abhimanyu Siwach <128322948+siwachabhi@users.noreply.github.com>

Author: siwachabhi

src/bedrock_agentcore_starter_toolkit/utils/runtime/templates/Dockerfile.j2

@@ -25,7 +25,7 @@ RUN uv pip install -r {{ dependencies_file }}
 {% endif %}
 
 {% if observability_enabled %}
-RUN uv pip install aws-opentelemetry-distro>=0.10.1
+RUN uv pip install aws-opentelemetry-distro==0.12.2
 {% endif %}
 
 # Signal that this is running in Docker for host binding logic