Allow totalSupply() to be an external method in the ERC20 properties

slither/tools/properties/properties/ercs/erc20/properties/transfer.py

@@ -37,7 +37,7 @@ ERC20_Transferable = [
         name="crytic_less_than_total_ERC20Properties()",
         description="Balance of one user must be less or equal to the total supply.",
         content="""
-\t\treturn this.balanceOf(msg.sender) <= totalSupply();""",
+\t\treturn this.balanceOf(msg.sender) <= this.totalSupply();""",
         type=PropertyType.MEDIUM_SEVERITY,
         return_type=PropertyReturn.SUCCESS,
         is_unit_test=True,
@@ -48,7 +48,7 @@ ERC20_Transferable = [
         name="crytic_totalSupply_consistant_ERC20Properties()",
         description="Balance of the crytic users must be less or equal to the total supply.",
         content="""
-\t\treturn this.balanceOf(crytic_owner) + this.balanceOf(crytic_user) + this.balanceOf(crytic_attacker) <= totalSupply();""",
+\t\treturn this.balanceOf(crytic_owner) + this.balanceOf(crytic_user) + this.balanceOf(crytic_attacker) <= this.totalSupply();""",
         type=PropertyType.MEDIUM_SEVERITY,
         return_type=PropertyReturn.SUCCESS,
         is_unit_test=True,