[ci] Fix pattern for code changes (#17275)
## Summary
`**/*` only matches files in a subdirectory whereas `**` matches any
file at an arbitrary depth
> A trailing "/**" matches everything inside. For example, "abc/**"
matches all files inside directory "abc", relative to the location of
the .gitignore file, with infinite depth.
> A leading "**" followed by a slash means match in all directories. For
example, "**/foo" matches file or directory "foo" anywhere, the same as
pattern "foo". "**/foo/bar" matches file or directory "bar" anywhere
that is directly under directory "foo".
