doc: fix two instances of "the the" in godebug.md
Remove two instances of "the the" introduced recently
in CL 562343 and CL 562975.
Change-Id: Ib32ca80fcd6764343021c84135bd65853945c9ea
GitHub-Last-Rev:
0bd2c0b4bd662645d03fb4f08e201bae29c1a7e6
GitHub-Pull-Request: golang/go#67594
Reviewed-on: https://go-review.googlesource.com/c/go/+/587717
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@google.com>