revert YANG check in db_migrator (#3793)

What I did
revert YANG check in db_migrator

How I did it
revert

How to verify it
revert

Author: wen587

scripts/config_validator.py

@@ -6,7 +6,6 @@
 import sys
 import traceback
 import re
-import subprocess
 
 from sonic_py_common import device_info, logger
 from swsscommon.swsscommon import SonicV2Connector, ConfigDBConnector, SonicDBConfig
@@ -1368,34 +1367,6 @@ def migrate(self):
             version = next_version
         # Perform common migration ops
         self.common_migration_ops()
-        # Perform yang validation
-        self.validate()
-
-    def validate(self):
-        config = self.configDB.get_config()
-        # Fix table key in tuple
-        for table_name, table in config.items():
-            new_table = {}
-            hit = False
-            for table_key, table_val in table.items():
-                if isinstance(table_key, tuple):
-                    new_key = "|".join(table_key)
-                    new_table[new_key] = table_val
-                    hit = True
-                else:
-                    new_table[table_key] = table_val
-            if hit:
-                config[table_name] = new_table
-        config_file = "/tmp/validate.json"
-        with open(config_file, 'w') as fp:
-            json.dump(config, fp)
-        process = subprocess.Popen(["config_validator.py", "-c", config_file])
-        # Check validation result for unit test
-        # Check validation result for end to end test
-        mark_file = "/etc/sonic/mgmt_test_mark"
-        if os.environ.get("UTILITIES_UNIT_TESTING", "0") == "2" or os.path.exists(mark_file):
-            ret = process.wait()
-            assert ret == 0, "Yang validation failed"
 
 def main():
     try:

scripts/db_migrator.py

@@ -116,7 +116,6 @@
         'scripts/buffershow',
         'scripts/coredump-compress',
         'scripts/configlet',
-        'scripts/config_validator.py',
         'scripts/db_migrator.py',
         'scripts/decode-syseeprom',
         'scripts/dropcheck',