fix: Address alter_column warning for MSSQL (meltano#6643)

fix: Address state enum alter_column for MSSQL

src/meltano/migrations/versions/13e8639c6d2b_add_state_edit_to_job_state_enum.py

@@ -47,6 +47,7 @@ def upgrade():
             column_name="state",
             type_=sa.types.String(max_string_length),
             existing_type=sa.Enum(State, name="job_state"),
+            existing_nullable=True,
         )
 
     # In postgresql, drop the created Enum type so that