fix: correct Content-Length headers in email forward webhook fixtures (#926)

Fixes incorrect Content-Length headers in three email forward webhook fixtures that were causing test failures in client libraries.

Author: weppos

fixtures/v2/.gitattributes

@@ -0,0 +1,4 @@
+# Preserve line endings in HTTP fixture files
+# These files contain raw HTTP requests/responses. Treat them as binary
+# to prevent Git from converting line endings.
+**/*.http binary

fixtures/v2/webhooks/email_forward.create/example.http

@@ -6,7 +6,7 @@ user-agent: DNSimple-Webhook-Notifier/f152781ec87b328bf9edcaa760f0e5342bdd15cf
 content-type: application/json
 connect-time: 1
 via: 1.1 vegur
-content-length: 561
+content-length: 560
 total-route-time: 0
 connection: keep-alive
 

fixtures/v2/webhooks/email_forward.delete/example.http

@@ -1,6 +1,6 @@
 POST /1djlwbe1 HTTP/1.1
 host: example.com
-content-length: 551
+content-length: 550
 total-route-time: 0
 via: 1.1 vegur
 accept-encoding: gzip

fixtures/v2/webhooks/email_forward.update/example.http

@@ -1,6 +1,6 @@
 POST /1djlwbe1 HTTP/1.1
 host: example.com
-content-length: 551
+content-length: 550
 accept-encoding: gzip
 x-request-id: 42f14e6a-21e4-4942-9556-682298b5a852
 user-agent: DNSimple-Webhook-Notifier/f152781ec87b328bf9edcaa760f0e5342bdd15cf