Don't set serverity level for text log.

Author: liuyunnnn

src/logger.ts

@@ -142,9 +142,6 @@ export function getModifiedData(
     }
   } else {
     dataWithContext = getTextWithContext(processedData, currentContext);
-    if (stderr) {
-      dataWithContext[SEVERITY] = 'ERROR';
-    }
   }
 
   return JSON.stringify(dataWithContext) + '\n';

test/logger.ts

@@ -135,7 +135,7 @@ describe('getModifiedData', () => {
     const modifiedData = getModifiedData(sampleText, undefined, true);
     const expectedOutput =
       JSON.stringify(
-        Object.assign(JSON.parse(expectedTextOutput), {severity: 'ERROR'})
+        Object.assign(JSON.parse(expectedTextOutput))
       ) + '\n';
     assert.equal(modifiedData, expectedOutput);
   });