There is no way to revert your approval of a suggested edit. However, once a suggested edit gets approved (or rejected) you can always edit again to fix remaining problems.
In this case, I went ahead and edited to remove the italics and also fix remaining problems, like the title, other grammatical issues, and punctuation issues. I marked the suggested edit as helpful due to the fixes in other areas, but rejecting may arguably also have been a correct approach considering there were other areas left untended.
Ideally, suggested edits should fix all problems with a post, unless the edit fixes a major problem with the post, such as a title edit or clarifying something in the body of importance. Hope this helps.