Fix non-portable find -iname in verify-release-candidate.sh (#1613)

The SNAPSHOT check used `find -iname 'Cargo.toml'` without a starting
path. GNU find tolerates this, but BSD find (macOS) rejects it with
`find: illegal option -- i`. The error makes the piped `xargs grep`
receive no input and return non-zero, so the `if` silently evaluates
false and the SNAPSHOT check is skipped on macOS rather than running.

Add the explicit `.` starting path so the check works on both GNU and
BSD find.

Co-authored-by: Isaac

Author: viirya

dev/release/verify-release-candidate.sh

@@ -153,7 +153,7 @@ test_source_distribution() {
   #TODO: we should really run tests here as well
   #python3 -m pytest
 
-  if ( find -iname 'Cargo.toml' | xargs grep SNAPSHOT ); then
+  if ( find . -iname 'Cargo.toml' | xargs grep SNAPSHOT ); then
     echo "Cargo.toml version should not contain SNAPSHOT for releases"
     exit 1
   fi