Ensure list of reserved words are lowercased to align with check.

[jakehilton]

Environment details

• Programming language: Python
• OS: OSX
• Language runtime version: 3.11
• Package version: 1.5.0

Steps to reproduce

1. Start local spanner emulator with project and instance setup
2. Attempt to create a table using the "groups" reserved word that should be escaped
3. Exception is thrown because the word is not properly detected as needing to be escaped

Sample python code:
`
import os

from sqlalchemy import (
Column,
Integer,
MetaData,
String,
Table,
create_engine,
)

os.environ["SPANNER_EMULATOR_HOST"] = "localhost:9010"
os.environ["SQLALCHEMY_SILENCE_UBER_WARNING"] = "1"

engine = create_engine(
"spanner+spanner://localhost:9010/projects/test-project/instances/test-instance/databases/test-database"
)

print(engine)

metadata = MetaData(bind=engine)

user = Table(
'groups',
metadata,
Column("user_id", Integer, primary_key=True),
Column("user_name", String(16), nullable=False),
)

metadata.create_all(engine)

print("all created?")
`

Exception being thrown:
`Exception has occurred: InvalidArgument
400 Error parsing Spanner DDL statement: CREATE TABLE groups (
user_id INT64 NOT NULL,
user_name STRING(16) NOT NULL
) PRIMARY KEY (user_id) : Syntax error on line 1, column 14: Encountered 'groups' while parsing: identifier
grpc._channel._InactiveRpcError: <_InactiveRpcError of RPC that terminated with:
status = StatusCode.INVALID_ARGUMENT
details = "Error parsing Spanner DDL statement: CREATE TABLE groups (
user_id INT64 NOT NULL,
user_name STRING(16) NOT NULL
) PRIMARY KEY (user_id) : Syntax error on line 1, column 14: Encountered 'groups' while parsing: identifier"
debug_error_string = "UNKNOWN:Error received from peer {grpc_message:"Error parsing Spanner DDL statement: CREATE TABLE groups (\n\tuser_id INT64 NOT NULL, \n\tuser_name STRING(16) NOT NULL\n) PRIMARY KEY (user_id) : Syntax error on line 1, column 14: Encountered 'groups' while parsing: identifier", grpc_status:3, created_time:"2023-05-15T15:36:27.22146-06:00"}"

The above exception was the direct cause of the following exception:

File "/Users/me/repos/test/conntest.py", line 58, in
metadata.create_all(engine)
google.api_core.exceptions.InvalidArgument: 400 Error parsing Spanner DDL statement: CREATE TABLE groups (
user_id INT64 NOT NULL,
user_name STRING(16) NOT NULL
) PRIMARY KEY (user_id) : Syntax error on line 1, column 14: Encountered 'groups' while parsing: identifier`