terraform: remove main

A good main.tf acts as an entrypoint to a module and is typically used
when the module is smaller. For larger module it's best to split things
up and try to map the resources with the filename to make them easier to
find.

terraform/terraform_backend.tf

@@ -0,0 +1,6 @@
+terraform {
+  backend "remote" {
+    organization = "nix-community"
+    workspaces { name = "nix-community" }
+  }
+}

terraform/terraform_providers.tf

@@ -1,9 +1,4 @@
 terraform {
-  backend "remote" {
-    organization = "nix-community"
-    workspaces { name = "nix-community" }
-  }
-
   required_providers {
     cloudflare = {
       source = "cloudflare/cloudflare"