fix: use operation as fallback name when attemptSpanName is attempt

Author: jinseopkim0

sdk-platform-java/gax-java/gax/src/main/java/com/google/api/gax/tracing/OpenTelemetryTracingTracer.java

@@ -138,7 +138,7 @@ private static String resolveOperationSpanName(
       if (attemptSpanName.endsWith("/attempt")) {
         return attemptSpanName.substring(0, attemptSpanName.length() - "/attempt".length());
       }
-      return attemptSpanName;
+      return "attempt".equals(attemptSpanName) ? "operation" : attemptSpanName;
     }
     return "operation";
   }