remove problematic test cases (mutating in render fn)

test/unit/features/filter/filter.spec.js

@@ -113,24 +113,6 @@ describe('Filters', () => {
     expect(vm.$el.textContent).toBe(String(8))
   })
 
-  it('handle division with variable++', () => {
-    const vm = new Vue({
-      data: { a: 7 },
-      template: `<div>{{ a++ / 2 | double }}</div>`,
-      filters: { double: v => v * 2 }
-    }).$mount()
-    expect(vm.$el.textContent).toBe(String(7))
-  })
-
-  it('handle division with variable--', () => {
-    const vm = new Vue({
-      data: { a: 7 },
-      template: `<div>{{ a-- / 2 | double }}</div>`,
-      filters: { double: v => v * 2 }
-    }).$mount()
-    expect(vm.$el.textContent).toBe(String(7))
-  })
-
   it('handle division with variable_', () => {
     const vm = new Vue({
       data: { a_: 8 },