Update docs/configuration.md

Co-authored-by: per1234 <[email protected]>

Author: cmaglie

Diff for: docs/configuration.md

@@ -13,7 +13,7 @@
     user to install them, but with the lowest priority over other installed libraries with the same name, it's the
     equivalent of the Arduino IDE's bundled libraries directory.
   - `builtin.tools` - it's a list of directories of tools that will be available to all platforms without the need for
-    the user to install them, it's the equivalent of the Arduino IDE's bundled tools directory.
+    the user to install them, it's the equivalent of the Arduino IDE 1.x bundled tools directory.
 - `library` - configuration options relating to Arduino libraries.
   - `enable_unsafe_install` - set to `true` to enable the use of the `--git-url` and `--zip-file` flags with
     [`arduino-cli lib install`][arduino cli lib install]. These are considered "unsafe" installation methods because