Fix main build unit test failure (#208)

*Issue #, if available:*
-
https://github.com/aws-observability/aws-otel-js-instrumentation/actions/runs/16012481365/job/45173185314#step:4:1017

Main build sets `AWS_DEFAULT_REGION`, which changes a unit test result.

*Description of changes:*
Set/unset `AWS_DEFAULT_REGION` in tests where needed.


By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice.

Author: jj22ee

aws-distro-opentelemetry-node-autoinstrumentation/test/register.test.ts

@@ -30,6 +30,7 @@ describe('Register', function () {
       delete process.env.OTEL_NODE_DISABLED_INSTRUMENTATIONS;
 
       delete process.env.AWS_REGION;
+      delete process.env.AWS_DEFAULT_REGION;
       delete process.env.AGENT_OBSERVABILITY_ENABLED;
       delete process.env.OTEL_EXPORTER_OTLP_TRACES_ENDPOINT;
       delete process.env.OTEL_EXPORTER_OTLP_LOGS_ENDPOINT;
@@ -69,13 +70,23 @@ describe('Register', function () {
     });
 
     it('Configures with AgentObservabilityEnabled with set region', () => {
-      process.env.AWS_REGION = 'us-west-2';
       process.env.AGENT_OBSERVABILITY_ENABLED = 'true';
+      process.env.AWS_REGION = 'us-west-2';
 
       setAwsDefaultEnvironmentVariables();
 
       expect(process.env.OTEL_EXPORTER_OTLP_TRACES_ENDPOINT).toEqual('https://xray.us-west-2.amazonaws.com/v1/traces');
       expect(process.env.OTEL_EXPORTER_OTLP_LOGS_ENDPOINT).toEqual('https://logs.us-west-2.amazonaws.com/v1/logs');
+
+      delete process.env.AWS_REGION;
+      delete process.env.OTEL_EXPORTER_OTLP_TRACES_ENDPOINT;
+      delete process.env.OTEL_EXPORTER_OTLP_LOGS_ENDPOINT;
+      process.env.AWS_DEFAULT_REGION = 'us-east-2';
+
+      setAwsDefaultEnvironmentVariables();
+
+      expect(process.env.OTEL_EXPORTER_OTLP_TRACES_ENDPOINT).toEqual('https://xray.us-east-2.amazonaws.com/v1/traces');
+      expect(process.env.OTEL_EXPORTER_OTLP_LOGS_ENDPOINT).toEqual('https://logs.us-east-2.amazonaws.com/v1/logs');
     });
 
     it('Configures defaults when AgentObservabilityEnabled is true', () => {