Use uppercase for heading

Author: Luyao-Zhang-1

content/en/docs/refguide/runtime/metrics.md

@@ -366,7 +366,7 @@ The name must adhere to the following rules:
 It is recommended to use a common prefix that uniquely defines your organisation and application.
 {{% /alert %}}
 
-### 5.2 Deprecated usages
+### 5.2 Deprecated Usages
 
 The following deprecated usages will be removed in the future releases,