fix: rage4 - add error 400 and TXT cleanup

[aorith]

The following error happens if the header is set
to 'Content-Type: application/json':

    {"statusCode":400,"message":"One or more errors occurred!",
    "errors":{"serializerErrors":["The input does not contain
    any JSON tokens. Expected the input to start with a valid
    JSON token, when isFinalBlock is true. LineNumber:
    0 | BytePositionInLine: 0."]}}

Fix TXT removal

Hello,

So currently, the rage4 API is failing because we're sending the Content-Type: application/json, also the rm function is not retrieving the id correctly from the response.
This fixes both issues.

I understand that this PR won't be merged since it doesn't comply with https://github.com/acmesh-official/acme.sh/wiki/DNS-API-Test but I do not have the time or a Rage4 account that I can use for this (but I've tested this fix at my job and it does work). Maybe someone can run the CI/CD tests.

[github-actions]

Welcome
First thing: don't send PR to the master branch, please send to the dev branch instead.
Please make sure you've read our DNS API Dev Guide and DNS-API-Test.
Then reply on this message, otherwise, your code will not be reviewed or merged.
We look forward to reviewing your Pull request shortly ✨
注意: 必须通过了 DNS-API-Test 才会被 review. 无论是修改, 还是新加的 dns api, 都必须确保通过这个测试.

[aorith]

Welcome First thing: don't send PR to the master branch, please send to the dev branch instead. Please make sure you've read our DNS API Dev Guide and DNS-API-Test. Then reply on this message, otherwise, your code will not be reviewed or merged. We look forward to reviewing your Pull request shortly ✨ 注意: 必须通过了 DNS-API-Test 才会被 review. 无论是修改, 还是新加的 dns api, 都必须确保通过这个测试.

👍