refactor: use with statement for file reading (#2740)

## Changes

This PR updates the file reading logic to use a with statement, aligning
with Python best practices for resource management. is a minor change
but ensures consistency with the project standard, as other parts
already use with statements.

Co-authored-by: Denis Bilenko <denis.bilenko@databricks.com>

Author: allrob23

tools/validate_whitespace.py

@@ -71,7 +71,8 @@ def main():
         if f in ignores:
             n_skipped += 1
             continue
-        data = open(f, "rb").read()
+        with open(f, "rb") as file:
+            data = file.read()
         error = False
         for msg in validate_contents(data):
             print(f"{f}:{msg}")