fix: gzip plugin schema typo (#2142)

diff --git a/api/conf/schema.json b/api/conf/schema.json
index 2fbbeed..76f1fb8 100644
--- a/api/conf/schema.json
+++ b/api/conf/schema.json
@@ -3141,7 +3141,7 @@
 								"minLength": 1,
 								"type": "string"
 							},
-							"minItem": 1,
+							"minItems": 1,
 							"type": "array"
 						}, {
 							"enum": ["*"]