[M140] Disable SerialSplitDtrAndRts by default

Original change's description:
> Disable SerialSplitDtrAndRts by default
> 
> step 1 of go/finch-killswitch#process
> 
> Bug: 437068905
> Change-Id: I8a3cfe21a23894ee470d6f625fabdefd67e624ec
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6828531
> Reviewed-by: Alvin Ji <alvinji@chromium.org>
> Commit-Queue: Jack Hsieh <chengweih@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1498892}

Bug: 437969261,437068905
Change-Id: I8a3cfe21a23894ee470d6f625fabdefd67e624ec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6838501
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Chrome Cherry Picker <chrome-cherry-picker@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/7339@{#404}
Cr-Branched-From: 27be8b77710f4405fdfeb4ee946fcabb0f6c92b2-refs/heads/main@{#1496484}
diff --git a/services/device/public/cpp/device_features.cc b/services/device/public/cpp/device_features.cc
index ea06039..6b22725 100644
--- a/services/device/public/cpp/device_features.cc
+++ b/services/device/public/cpp/device_features.cc
@@ -155,7 +155,7 @@
 // Can be disabled as a kill switch if needed.
 BASE_FEATURE(kSerialSplitDtrAndRts,
              "SerialSplitDtrAndRts",
-             base::FEATURE_ENABLED_BY_DEFAULT);
+             base::FEATURE_DISABLED_BY_DEFAULT);
 #endif  // !BUILDFLAG(IS_WIN)
 
 }  // namespace features