fix: Modify the incorrect configuration name for Google storage (#5595)

Co-authored-by: Wenming Pan <pwm@google.com>

api/.env.example

@@ -39,7 +39,7 @@ DB_DATABASE=dify
 
 # Storage configuration
 # use for store upload files, private keys...
-# storage type: local, s3, azure-blob
+# storage type: local, s3, azure-blob, google-storage
 STORAGE_TYPE=local
 STORAGE_LOCAL_PATH=storage
 S3_USE_AWS_MANAGED_IAM=false
@@ -63,7 +63,7 @@ ALIYUN_OSS_REGION=your-region
 
 # Google Storage configuration
 GOOGLE_STORAGE_BUCKET_NAME=yout-bucket-name
-GOOGLE_STORAGE_SERVICE_ACCOUNT_JSON=your-google-service-account-json-base64-string
+GOOGLE_STORAGE_SERVICE_ACCOUNT_JSON_BASE64=your-google-service-account-json-base64-string
 
 # Tencent COS Storage configuration
 TENCENT_COS_BUCKET_NAME=your-bucket-name