docs: fix $lt and $gt in api reference (#8580)

www/apps/api-reference/app/_mdx/admin.mdx

@@ -331,7 +331,7 @@ For example:
 
 
 ```bash
-curl -g "http://localhost:9000/admin/products?created_at[lt]=2023-02-17" \
+curl -g "http://localhost:9000/admin/products?created_at[$lt]=2023-02-17" \
 -H 'Authorization: Bearer {jwt_token}'
 ```
 
@@ -344,7 +344,7 @@ For example:
 
 
 ```bash
-curl -g "http://localhost:9000/admin/products?created_at[lt]=2023-02-17T07:22:30Z" \
+curl -g "http://localhost:9000/admin/products?created_at[$lt]=2023-02-17T07:22:30Z" \
 -H 'Authorization: Bearer {jwt_token}'
 ```
 
@@ -382,7 +382,7 @@ For example:
 
 
 ```bash
-curl -g "http://localhost:9000/admin/products?created_at[lt]=2023-02-17&created_at[gt]=2022-09-17" \
+curl -g "http://localhost:9000/admin/products?created_at[$lt]=2023-02-17&created_at[$gt]=2022-09-17" \
 -H 'Authorization: Bearer {jwt_token}'
 ```
 

www/apps/api-reference/app/_mdx/store.mdx

@@ -348,7 +348,7 @@ For example:
 
 
 ```bash
-curl -g "http://localhost:9000/store/products?created_at[lt]=2023-02-17"
+curl -g "http://localhost:9000/store/products?created_at[$lt]=2023-02-17"
 ```
 
 
@@ -360,7 +360,7 @@ For example:
 
 
 ```bash
-curl -g "http://localhost:9000/store/products?created_at[lt]=2023-02-17T07:22:30Z"
+curl -g "http://localhost:9000/store/products?created_at[$lt]=2023-02-17T07:22:30Z"
 ```
 
 
@@ -396,7 +396,7 @@ For example:
 
 
 ```bash
-curl -g "http://localhost:9000/store/products?created_at[lt]=2023-02-17&created_at[gt]=2022-09-17"
+curl -g "http://localhost:9000/store/products?created_at[$lt]=2023-02-17&created_at[$gt]=2022-09-17"
 ```
 
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