docs: small typo in an example (#5456)

Hello :)

The exported field for local.file is `content` and not `content`. :)

https://grafana.com/docs/agent/latest/flow/reference/components/local.file/#exported-fields

Co-authored-by: Clayton Cornell <[email protected]>
(cherry picked from commit 73c2642)

docs/sources/flow/config-language/expressions/function_calls.md

@@ -25,7 +25,7 @@ allow for more complex expressions (e.g. concatenating arrays or decoding JSON
 strings into objects).
 ```river
 env("HOME")
-json_decode(local.file.cfg.contents)["namespace"]
+json_decode(local.file.cfg.content)["namespace"]
 ```
 
 [standard library]: {{< relref "../../reference/stdlib" >}}