chore(internal/godocfx): add binary to .gitignore (#4296)

diff --git a/internal/godocfx/.gitignore b/internal/godocfx/.gitignore
index 723fd50..cad9d41 100644
--- a/internal/godocfx/.gitignore
+++ b/internal/godocfx/.gitignore
@@ -1,4 +1,4 @@
 obj/
 site/
-docfxgen
+godocfx
 testdata/out/