Fixed JSON capitalization

Author: tcerqueira-cf

src/content/docs/learning-paths/secure-internet-traffic/build-dns-policies/create-list.mdx

@@ -24,7 +24,7 @@ The following DNS policy will allow access to all approved corporate domains inc
 	```sh
 curl --request POST \
   --url https://api.cloudflare.com/client/v4/accounts/{account_id}/gateway/rules \
-  --header 'Content-Type: application/json' \
+  --header 'Content-Type: application/JSON' \
   --header "Authorization: Bearer <API TOKEN>" \
 	--data '{
   "name": "All-DNS-CorporateDomain-AllowList",

src/content/docs/learning-paths/secure-internet-traffic/build-dns-policies/create-policy.mdx

@@ -33,7 +33,7 @@ To create a new DNS policy using **cURL**:
 	```sh
 	curl --request POST \
 	  --url https://api.cloudflare.com/client/v4/accounts/{account_id}/gateway/rules \
-	  --header 'Content-Type: application/json' \
+	  --header 'Content-Type: application/JSON' \
 	  --header "Authorization: Bearer <API_TOKEN>" \
 		--data '{
 		"name": "All-DNS-SecurityCategories-Blocklist",

src/content/docs/learning-paths/secure-internet-traffic/build-dns-policies/recommended-dns-policies.mdx

@@ -24,7 +24,7 @@ Allowlist any known domains and hostnames. With this policy, you ensure that you
 ```sh
 curl --request POST \
   --url https://api.cloudflare.com/client/v4/accounts/{account_id}/gateway/rules \
-  --header 'Content-Type: application/json' \
+  --header 'Content-Type: application/JSON' \
   --header "Authorization: Bearer <API TOKEN>" \
 	--data '{
   "name": "All-DNS-Domain-Allowlist",