importing line amount for percussion in guitar pro

[alexpavlov96]

Resolves: (direct link to the issue)

(short description of the changes and the motivation to make the changes)

• [ ] I signed CLA
• [ ] I made sure the code in the PR follows the coding rules
• [ ] I made sure the code compiles on my machine
• [ ] I made sure there are no unnecessary changes in the code
• [ ] I made sure the title of the PR reflects the core meaning of the issue you are solving
• [ ] I made sure the commit message(s) contain a description and answer the question "Why do those changes fix that particular issue?" or "Why are those changes really necessary as improvements?"
• [ ] I made sure the commit message title starts with "fix #424242:" if there is a related issue
• [ ] I created the test (mtest, vtest, script test) to verify the changes I made