PrettyPrint: last comment is removed for user definitions

If we try to pretty print those user definitions:
```
MyNF=Pi()/2; // Half PI
```
The last comment will be deleted.

Test file: FormatterTests.cs; test method: TestUserDefinitionsPrettyPrint
```
[InlineData("MyNF=Pi()/2; // Half PI", "MyNF = Pi() / 2; // Half PI")]
```