dns_porkbun: remove stray backslashes

[allddd]

With grep 3.11, the following warnings are displayed while removing DNS records via Porkbun API:

user@server ~ $ acme.sh --issue --dns dns_porkbun -d domain.xyz -d '*.domain.xyz'
[...]
[2024-07-18T19:34:14 UTC] Getting webroot for domain='domain.xyz'
[2024-07-18T19:34:14 UTC] Getting webroot for domain='*.domain.xyz'
[2024-07-18T19:34:14 UTC] Adding TXT value: Z3JyZ8zPbPPeeC7K9pkqmEDEhIIoq0yBVlS0s_NdPIk for domain: _acme-challenge.domain.xyz
[2024-07-18T19:34:24 UTC] Adding record
[2024-07-18T19:34:30 UTC] Added, OK
[2024-07-18T19:34:30 UTC] The TXT record has been successfully added.
[2024-07-18T19:34:30 UTC] Adding TXT value: UhS2FMC8PGJ4PeBfJGyGiMircuPxINyvEs_bTJpfXs8 for domain: _acme-challenge.domain.xyz
[2024-07-18T19:34:40 UTC] Adding record
[2024-07-18T19:34:46 UTC] Added, OK
[2024-07-18T19:34:46 UTC] The TXT record has been successfully added.
[2024-07-18T19:34:46 UTC] Let's check each DNS record now. Sleeping for 20 seconds first.
[2024-07-18T19:35:07 UTC] You can use '--dnssleep' to disable public dns checks.
[2024-07-18T19:35:07 UTC] See: https://github.com/acmesh-official/acme.sh/wiki/dnscheck
[2024-07-18T19:35:07 UTC] Checking domain.xyz for _acme-challenge.domain.xyz
[2024-07-18T19:35:08 UTC] Success for domain domain.xyz '_acme-challenge.domain.xyz'.
[2024-07-18T19:35:08 UTC] Checking domain.xyz for _acme-challenge.domain.xyz
[2024-07-18T19:35:08 UTC] Success for domain domain.xyz '_acme-challenge.domain.xyz'.
[2024-07-18T19:35:08 UTC] All checks succeeded
[2024-07-18T19:35:08 UTC] Verifying: domain.xyz
[2024-07-18T19:35:09 UTC] Processing. The CA is processing your order, please wait. (1/30)
[...]
[2024-07-18T19:36:56 UTC] Removing DNS records.
[2024-07-18T19:36:56 UTC] Removing txt: Z3JyZ8zPbPPeeC7K9pkqmEDEhIIoq0yBVlS0s_NdPIk for domain: _acme-challenge.domain.xyz
grep: warning: stray \ before "
grep: warning: stray \ before "
[2024-07-18T19:37:12 UTC] Successfully removed
[2024-07-18T19:37:12 UTC] Removing txt: UhS2FMC8PGJ4PeBfJGyGiMircuPxINyvEs_bTJpfXs8 for domain: _acme-challenge.domain.xyz
grep: warning: stray \ before "
grep: warning: stray \ before "
[2024-07-18T19:37:28 UTC] Successfully removed
[...]

I have tested this patch with grep 3.11 and 3.8 and it gets rid of the warnings without affecting functionality.

[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.

[allddd]

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.

👍