Don't force uppercase on ruleSeverity (#2507)

src/language/rule/rule.ts

@@ -342,7 +342,7 @@ export class RuleFailure {
                     : this.fix.toJson(),
             name: this.fileName,
             ruleName: this.ruleName,
-            ruleSeverity: this.ruleSeverity.toUpperCase(),
+            ruleSeverity: this.ruleSeverity,
             startPosition: this.startPosition.toJson(),
         };
     }

test/formatters/jsonFormatterTests.ts

@@ -73,7 +73,7 @@ describe("JSON Formatter", () => {
                     character: 1,
                 },
                 ruleName: "first-name",
-                ruleSeverity: "ERROR",
+                ruleSeverity: "error",
             },
             {
                 name: TEST_FILE,
@@ -110,9 +110,10 @@ describe("JSON Formatter", () => {
                     character: 0,
                 },
                 ruleName: "full-name",
-                ruleSeverity: "ERROR",
+                ruleSeverity: "error",
             },
         ];
+
         /* tslint:enable:object-literal-sort-keys */
 
         const actualResult = JSON.parse(formatter.format(failures));