[BUG][aspnetcore] Resolve Conflict between Program.cs and launchProfile

Description

There are multiple ways to specify the hosting Url for an aspnetcore application:

1. Specifying it via Environment Variables
2. Specifying it during development via launchProfiles
3. Specifying it in code (Overwriting any other settings)

Currently the generator uses option 3:
https://github.com/OpenAPITools/openapi-generator/blob/5b6b4c9d4829b57716741dc35b3f1033e5483784/modules/openapi-generator/src/main/resources/aspnetcore/3.0/Program.mustache#L30

Which in my opinion is not alright, because as stated in the README.md:
https://github.com/OpenAPITools/openapi-generator/blob/5b6b4c9d4829b57716741dc35b3f1033e5483784/modules/openapi-generator/src/main/resources/aspnetcore/3.0/build.bat.mustache#L8

We should be able to use the launchProfiles. But as it is coded into the program it will always use serverPort.

Suggest a fix

Remove the line and maybe add a documentation link on how to setup the right port.

Start with modules/openapi-generator/src/main/resources/aspnetcore/3.0/Program.mustache, especially the hosting URL line linked in the issue, and compare it with Properties/launchSettings.json and the README reference in build.bat.mustache. Done means launchProfiles can determine the development port instead of always being overridden by serverPort.