BUG: "Import template" don't work for removing extra styles

https://grapesjs.com/demo.html

### Describe the bug

**How to reproduce the bug?**
1. Add paragraph block
2. Open "Import template" and add these lines and press "Import"
`  h1, h2, h3, h4, h5, h6{
    font-family:Arial, Helvetica, sans-serif;
    line-height:1.5;
  }
  p, span, div{
    font-family:Arial, Helvetica, sans-serif;
    line-height:1.5;
    color:red;
  }`
3. The imported codes working correctly
4. Now open "Import template" and remove those lines that added before and press "Import"
5. If you open "Import template" again you can see those codes yet and it is not possible to remove them at all, while we can add/remove styles related to blocks and components that have id for example:
`  #issu{
    padding:10px;
  }`


https://user-images.githubusercontent.com/65819265/169222606-bd95f54b-8428-4c02-98f0-d702cfa28512.mp4


Is it a bug or a normal behavior? if It is not a bug is there any solution?


**What is the expected behavior?**
The extra styles should be removed after press "Import"

**What is the current behavior?**
The extra styles can be removed



### Code of Conduct

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