use correct header

scm-ui/src/repos/sources/components/content/SourcecodeViewer.js

@@ -111,7 +111,7 @@ export function getProgrammingLanguage(url: string) {
   return apiClient
     .head(url)
     .then(response => {
-      return { language: response.headers.get("Language") };
+      return { language: response.headers.get("X-Programming-Language") };
     })
     .catch(err => {
       return { error: err };

scm-ui/src/repos/sources/components/content/SourcecodeViewer.test.js

@@ -25,7 +25,7 @@ describe("get content", () => {
 
   it("should return language", done => {
     let headers = {
-      Language: "JAVA"
+      "X-Programming-Language": "JAVA"
     };
 
     fetchMock.head("/api/v2" + CONTENT_URL, {