docs: Document GoVersionOverride in configuration.md (#2444)

Updated `docs/configuration.md` to include a section on
`GoVersionOverride`, explaining its purpose and providing an example.

---
*PR created automatically by Jules for task
[4075414825524292983](https://jules.google.com/task/4075414825524292983)
started by @another-rex*

---------

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
Co-authored-by: Rex P <[email protected]>

Author: google-labs-jules[bot]

docs/configuration.md

@@ -95,3 +95,14 @@ ignore = true
 
 # ... and so on
 ```
+
+## Go Version Override
+
+Use the `GoVersionOverride` key to override the Go version used for scanning. This is useful when the scanner fails to detect the correct Go version or when you want to force a specific version.
+
+### Example
+
+```toml
+# Do not add a prefix (e.g. go1.20.0 is just 1.20.0)
+GoVersionOverride = "1.20.0"
+```