Udpate maven-badges to link to sonatype central (#349)

Missed updating these in #322

Author: psx95

exporters/auto/README.md

@@ -75,5 +75,5 @@ java -javaagent:path/to/opentelemetry-javaagent.jar \
 
 [autooconf]: https://github.com/open-telemetry/opentelemetry-java/tree/main/sdk-extensions/autoconfigure
 [auto-extensions]: https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/examples/extension/README.md
-[maven-image]: https://maven-badges.herokuapp.com/maven-central/com.google.cloud.opentelemetry/exporter-auto/badge.svg
+[maven-image]: https://img.shields.io/maven-central/v/com.google.cloud.opentelemetry/exporter-auto?color=dark-green
 [maven-url]: https://maven-badges.herokuapp.com/maven-central/com.google.cloud.opentelemetry/exporter-auto

exporters/metrics/README.md

@@ -75,5 +75,5 @@ MeterProvider provider = SdkMeterProvider.builder()
 
 
 
-[maven-image]: https://maven-badges.herokuapp.com/maven-central/com.google.cloud.opentelemetry/exporter-metrics/badge.svg
+[maven-image]: https://img.shields.io/maven-central/v/com.google.cloud.opentelemetry/exporter-metrics?color=dark-green
 [maven-url]: https://maven-badges.herokuapp.com/maven-central/com.google.cloud.opentelemetry/exporter-metrics

exporters/trace/README.md

@@ -130,5 +130,5 @@ TraceConfiguration.builder()
   - Learn more about Google Cloud Trace at https://cloud.google.com/trace
 
 
-[maven-image]: https://maven-badges.herokuapp.com/maven-central/com.google.cloud.opentelemetry/exporter-trace/badge.svg
+[maven-image]: https://img.shields.io/maven-central/v/com.google.cloud.opentelemetry/exporter-trace?color=dark-green
 [maven-url]: https://maven-badges.herokuapp.com/maven-central/com.google.cloud.opentelemetry/exporter-trace

propagators/gcp/README.md

@@ -39,5 +39,5 @@ public class MyMain {
 }
 ```
 
-[maven-image]: https://maven-badges.herokuapp.com/maven-central/com.google.cloud.opentelemetry/propagators-gcp/badge.svg
+[maven-image]: https://img.shields.io/maven-central/v/com.google.cloud.opentelemetry/propagators-gcp?color=dark-green
 [maven-url]: https://maven-badges.herokuapp.com/maven-central/com.google.cloud.opentelemetry/propagators-gcp