fix(checkbox): remove autocomplete attribute (#3377)

This attribute is yet to be supported by specs.

See: https://git.io/JesTb
Related issue/fix in Bootstrap twbs/bootstrap#28623  https://github.com/twbs/bootstrap/pullrequests/28952

src/buttons/checkbox.spec.ts

@@ -172,6 +172,22 @@ describe('NgbCheckBox', () => {
        }));
   });
 
+  describe('auto attributes', () => {
+
+    it('should not have autocomplete attribute set to off', () => {
+      const fixture = createTestComponent(`
+        <label ngbButtonLabel>
+          <input type="checkbox" ngbButton>
+        </label>
+      `);
+
+      fixture.detectChanges();
+      const input = fixture.debugElement.nativeElement.querySelector('input');
+      expect(input.getAttribute('autocomplete')).toBeNull();
+    });
+
+  });
+
 });
 
 @Component({selector: 'test-cmp', template: ''})

src/buttons/checkbox.ts

@@ -19,7 +19,6 @@ const NGB_CHECKBOX_VALUE_ACCESSOR = {
 @Directive({
   selector: '[ngbButton][type=checkbox]',
   host: {
-    'autocomplete': 'off',
     '[checked]': 'checked',
     '[disabled]': 'disabled',
     '(change)': 'onInputChange($event)',