Remove global flash message

Per our design docs, global flash messages aren't appropriate
in this context (or virtually anywhere!), so there's no reason
to catch this error here.

app/assets/javascripts/diffs/store/actions.js

@@ -656,11 +656,6 @@ export function switchToFullDiffFromRenamedFile({ commit, dispatch, state }, { d
       commit(types.SET_CURRENT_VIEW_DIFF_FILE_LINES, { filePath: diffFile.file_path, lines });
 
       dispatch('startRenderDiffsQueue');
-    })
-    .catch(error => {
-      dispatch('receiveFullDiffError', diffFile.file_path);
-
-      throw error;
     });
 }
 

spec/frontend/diffs/store/actions_spec.js

@@ -1255,7 +1255,6 @@ describe('DiffsStoreActions', () => {
 
   describe('switchToFullDiffFromRenamedFile', () => {
     const SUCCESS_URL = 'fakehost/context.success';
-    const ERROR_URL = 'fakehost/context.error';
     const testFilePath = 'testpath';
     const updatedViewerName = 'testviewer';
     const preparedLine = { prepared: 'in-a-test' };
@@ -1311,27 +1310,6 @@ describe('DiffsStoreActions', () => {
         },
       );
     });
-
-    describe('error', () => {
-      beforeEach(() => {
-        renamedFile = { ...testFile, context_lines_path: ERROR_URL };
-        mock.onGet(ERROR_URL).reply(500);
-      });
-
-      it('dispatches the error handling action', () => {
-        const rejected = testAction(
-          switchToFullDiffFromRenamedFile,
-          { diffFile: renamedFile },
-          null,
-          [],
-          [{ type: 'receiveFullDiffError', payload: testFilePath }],
-        );
-
-        return rejected.catch(error =>
-          expect(error).toEqual(new Error('Request failed with status code 500')),
-        );
-      });
-    });
   });
 
   describe('setFileCollapsed', () => {