_content/blog: update GODEBUG documentation to clarify go.work behavior

This change updates the documentation to explain how GODEBUG settings are configured based on the Go version specified in either the go.mod or go.work file, with go.work taking priority. This clarification helps developers understand the interaction of GODEBUG settings with different Go workspace configurations. Fixes golang/go#70083

Author: chansuke

_content/blog/compat.md

@@ -461,12 +461,13 @@ For the remaining programs, the new approach is:
  `/godebug/non-default-behavior/http2client:events` counts the
  number of HTTP transports that the program has configured without HTTP/2 support.
 
- 4. A program’s GODEBUG settings are configured to match the Go version
- listed in the main package’s `go.mod` file.
- If your program’s `go.mod` file says `go 1.20` and you update to
- a Go 1.21 toolchain, any GODEBUG-controlled behaviors changed in
- Go 1.21 will retain their old Go 1.20 behavior until you change the
- `go.mod` to say `go 1.21`.
+4. A program’s GODEBUG settings are configured to match the Go version
+ listed in either the main package's `go.mod` file or in a `go.work` file,
+ with the `go.work` file taking priority if both are present.
+ If your program's `go.mod` file says `go 1.20` (or the `go.work` file specifies `go 1.20`)
+ and you update to a Go 1.21 toolchain, any GODEBUG-controlled behaviors
+ changed in Go 1.21 will retain their old Go 1.20 behavior until you update
+ the relevant `go.mod` or `go.work` file to say `go 1.21`.
 
  5. A program can change individual GODEBUG settings by using `//go:debug` lines
  in package `main`.