sdk: Update documentation to point to v4.1

Update documentation to point to v4.1 and add a tip about Change-Ids in
merge commits.

Change-Id: I37e47ebc75ade6010f50133d063260b09736cb70

docs/instrumentation/tracing-sdk.md

diff --git a/docs/instrumentation/tracing-sdk.md b/docs/instrumentation/tracing-sdk.md
index f156bcf..66bf823 100644
--- a/docs/instrumentation/tracing-sdk.md
+++ b/docs/instrumentation/tracing-sdk.md
@@ -29,8 +29,8 @@
 
 To start using the Client API, first check out the latest SDK release:
 
-```sh
-git clone https://android.googlesource.com/platform/external/perfetto -b v4.0
+```bash
+git clone https://android.googlesource.com/platform/external/perfetto -b v4.1
 ```
 
 The SDK consists of two files, `sdk/perfetto.h` and `sdk/perfetto.cc`. These are