Revert "api: up emerge backtrack limit from 30 to 50"

This reverts commit b4c2c0bbd3d064a87be4c2505aaf54a55d1625e5.

Reason for revert: does not fix b/296792476

Original change's description:
> api: up emerge backtrack limit from 30 to 50
>
> BUG=b:296792476
> TEST=yolo
>
> Change-Id: I22f6f0ed2084a8b9e80ccb2d3b1fc9a3ed18caf7
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4807718
> Tested-by: Sergey Frolov <sfrolov@google.com>
> Auto-Submit: Sergey Frolov <sfrolov@google.com>
> Commit-Queue: Mike Frysinger <vapier@chromium.org>
> Reviewed-by: Mike Frysinger <vapier@chromium.org>
> Commit-Queue: Sergey Frolov <sfrolov@google.com>

BUG=b:296792476

Change-Id: If89c2b669f54fa7c7761b0b02637740fdd1e1013
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4834468
Reviewed-by: Alex Klein <saklein@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Sergey Frolov <sfrolov@google.com>
diff --git a/api/controller/sysroot.py b/api/controller/sysroot.py
index 2797bd3..a1b60f0 100644
--- a/api/controller/sysroot.py
+++ b/api/controller/sysroot.py
@@ -27,7 +27,7 @@
 
 _ACCEPTED_LICENSES = "@CHROMEOS"
 
-DEFAULT_BACKTRACK = 50
+DEFAULT_BACKTRACK = 30
 
 
 def _GetGomaLogDirectory():