docs: clarify nolintlint.allow-unused (golangci#2319)

Author: extemporalgenome

.golangci.example.yml

@@ -523,7 +523,7 @@ linters-settings:
     block-size: 1
 
   nolintlint:
-    # Enable to ensure that nolint directives are all used. Default is true.
+    # Disable to ensure that all nolint directives actually have an effect. Default is true.
     allow-unused: false
     # Disable to ensure that nolint directives don't have a leading space. Default is true.
     allow-leading-space: true