[docs][easy] Fix missing code block type in ruby.md (#1065)

## Summary

TSIA

## How was it tested?

Signed-off-by: Mike Landau <[email protected]>

Author: mikeland73

docs/app/docs/devbox_examples/languages/ruby.md

@@ -47,6 +47,6 @@ In case you are using bundler to install gems, bundler config file can still be
 
 `.bundle/config` file example:
 
-```
+```dotenv
 BUNDLE_BUILD__SASSC: "--disable-lto"
 ```