Bump versions.opentelemetry from 1.19.0 to 1.20.0 in /examples/extension (open-telemetry#7142)

Author: dependabot[bot]

examples/extension/build.gradle

@@ -23,7 +23,7 @@ version '1.0'
 ext {
   versions = [
     // these lines are managed by .github/scripts/update-sdk-version.sh
-    opentelemetry              : "1.19.0",
+    opentelemetry              : "1.20.0",
     opentelemetryAlpha         : "1.18.0-alpha",
 
     // these lines are managed by .github/scripts/update-version.sh