core/vm: fix comment grammar (#19923)

* core/vm:modify comment errors

* modify its back to it's

core/vm/contract.go

@@ -162,7 +162,7 @@ func (c *Contract) Address() common.Address {
 	return c.self.Address()
 }
 
-// Value returns the contracts value (sent to it from it's caller)
+// Value returns the contract's value (sent to it from it's caller)
 func (c *Contract) Value() *big.Int {
 	return c.value
 }