docs: fix link to py_reconfig and sh_py_run_test files (#2901)

Our test files aren't part of the sphinx docs, so use the gh-path
external link hook to
link to the files directly on github.

docs/devguide.md

diff --git a/docs/devguide.md b/docs/devguide.md
index 4d88b28..f233611 100644
--- a/docs/devguide.md
+++ b/docs/devguide.md
@@ -39,7 +39,7 @@
 
 ### sh_py_run_test
 
-The [`sh_py_run_test`](tests/support/sh_py_run_test.bzl) rule is a helper to
+The {gh-path}`sh_py_run_test <tests/support/sh_py_run_test.bzl` rule is a helper to
 make it easy to run a Python program with custom build settings using a shell
 script to perform setup and verification. This is best to use when verifying
 behavior needs certain environment variables or directory structures to
@@ -56,6 +56,8 @@
 verifying behavior that requires specific flags to be set and when the program
 itself can verify the desired state.
 
+They are located in {gh-path}`tests/support/py_reconfig.bzl`
+
 When adding a test, you may find the flag you need to set isn't supported by
 the rule. To have it support setting a new flag: