vendor: update buildkit to v0.19.0-rc1

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

vendor/go.opentelemetry.io/otel/RELEASING.md

@@ -69,6 +69,7 @@ Update go.mod for submodules to depend on the new release which will happen in t
        ```
 
    - Move all the `Unreleased` changes into a new section following the title scheme (`[<new tag>] - <date of release>`).
+   - Make sure the new section is under the comment for released section, like `<!-- Released section -->`, so it is protected from being overwritten in the future.
    - Update all the appropriate links at the bottom.
 
 4. Push the changes to upstream and create a Pull Request on GitHub.
@@ -110,17 +111,6 @@ It is critical you make sure the version you push upstream is correct.
 Finally create a Release for the new `<new tag>` on GitHub.
 The release body should include all the release notes from the Changelog for this release.
 
-## Verify Examples
-
-After releasing verify that examples build outside of the repository.
-
-```
-./verify_examples.sh
-```
-
-The script copies examples into a different directory removes any `replace` declarations in `go.mod` and builds them.
-This ensures they build with the published release, not the local copy.
-
 ## Post-Release
 
 ### Contrib Repository