Fix typo in exported param type name. (#7295)

Closes #7125.

Author: tseaver

spanner/google/cloud/spanner_v1/param_types.py

@@ -20,7 +20,7 @@
 # Scalar parameter types
 STRING = type_pb2.Type(code=type_pb2.STRING)
 BYTES = type_pb2.Type(code=type_pb2.BYTES)
-BOOE = type_pb2.Type(code=type_pb2.BOOL)
+BOOL = type_pb2.Type(code=type_pb2.BOOL)
 INT64 = type_pb2.Type(code=type_pb2.INT64)
 FLOAT64 = type_pb2.Type(code=type_pb2.FLOAT64)
 DATE = type_pb2.Type(code=type_pb2.DATE)