chore(): Fix minor typos in test descriptions (angular#2251)

Author: NothingEverHappens

src/auth/auth.spec.ts

@@ -71,7 +71,7 @@ describe('AngularFireAuth', () => {
     });
   });
 
-  it('should be exist', () => {
+  it('should exist', () => {
     expect(afAuth instanceof AngularFireAuth).toBe(true);
   });
 

src/functions/functions.spec.ts

@@ -26,7 +26,7 @@ describe('AngularFireFunctions', () => {
     done();
   });
 
-  it('should be exist', () => {
+  it('should exist', () => {
     expect(afFns instanceof AngularFireFunctions).toBe(true);
   });
 

src/performance/performance.spec.ts

@@ -25,12 +25,12 @@ describe('AngularFirePerformance', () => {
     done();
   });
 
-  it('should be exist', () => {
+  it('should exist', () => {
     expect(afp instanceof AngularFirePerformance).toBe(true);
   });
 
   it('should have the Performance instance', () => {
     expect(afp.performance).toBeDefined();
   });
 
-});
+});