fix acme renewal (#7409)

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### Tests

- I added test coverage for Go changes...
- [ ] in their respective `*_test.go` for unit tests.
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- I added test coverage for JavaScript changes...
- [ ] in `web_src/js/*.test.js` if it can be unit tested.
- [ ] in `tests/e2e/*.test.e2e.js` if it requires interactions with a live Forgejo server (see also the [developer guide for JavaScript testing](https://codeberg.org/forgejo/forgejo/src/branch/forgejo/tests/e2e/README.md#end-to-end-tests)).

### Documentation

- [ ] I created a pull request [to the documentation](https://codeberg.org/forgejo/docs) to explain to Forgejo users how to use this change.
- [x] I did not document these changes and I do not expect someone else to do it.

### Release notes

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Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/7409
Reviewed-by: Gusted <[e-mail]>
Co-authored-by: Gwendolyn <[e-mail]>
Co-committed-by: Gwendolyn <[e-mail]>

cmd/web_acme.go

···
 		altTLSALPNPort = p
 	}
 
-	magic := certmagic.NewDefault()
-	magic.Storage = &certmagic.FileStorage{Path: setting.AcmeLiveDirectory}
+	certmagic.Default.Storage = &certmagic.FileStorage{Path: setting.AcmeLiveDirectory}
+
 	// Try to use private CA root if provided, otherwise defaults to system's trust
 	var certPool *x509.CertPool
 	if setting.AcmeCARoot != "" {
···
 			log.Warn("Failed to parse CA Root certificate, using default CA trust: %v", err)
 		}
 	}
-	myACME := certmagic.NewACMEIssuer(magic, certmagic.ACMEIssuer{
+
+	certmagic.DefaultACME = certmagic.ACMEIssuer{
 		CA:                      setting.AcmeURL,
 		TrustedRoots:            certPool,
 		Email:                   setting.AcmeEmail,
···
 		ListenHost:              setting.HTTPAddr,
 		AltTLSALPNPort:          altTLSALPNPort,
 		AltHTTPPort:             altHTTPPort,
-	})
+	}
+
+	magic := certmagic.NewDefault()
+
+	myACME := certmagic.NewACMEIssuer(magic, certmagic.DefaultACME)
 
 	magic.Issuers = []certmagic.Issuer{myACME}