Bug fix in InjectHelper

UpdateParameterTypes() need to be called in order for newMethodDef to
get a ParameterList. Without doing this SimplifyMacros fails on methods
containing "ldarg" instruction.

https://github.com/0xd4d/dnlib/blob/master/src/DotNet/ParameterList.cs#L158

This caused issues when injecting methods such as Confuser.Runtime.Lzma.Decompress, turning
```
ldarg.0
```
into 
```
ldarg null
```
because of: https://github.com/0xd4d/dnlib/blob/master/src/DotNet/Emit/MethodUtils.cs#L97 which causes an exception in dnlib when writing method: https://github.com/0xd4d/dnlib/blob/master/src/DotNet/Writer/MethodBodyWriterBase.cs#L359