Address review feedback

Author: odeke-em

observability-test/spanner.ts

@@ -473,7 +473,7 @@ describe('EndToEnd', () => {
         database.formattedName_
       );
       await database.runTransactionAsync(async transaction => {
-        const [rows] = await transaction!.run('SELECT 1');
+        await transaction!.run('SELECT 1');
       });
 
       traceExporter.forceFlush();

src/database.ts

@@ -3395,7 +3395,7 @@ class Database extends common.GrpcServiceObject {
             try {
               return await runner.run();
             } catch (e) {
-              setSpanError(span, e as Error);
+              setSpanErrorAndException(span, e as Error);
               throw e;
             } finally {
               span.end();