Remove max connection limit ( -x, --max-connection-per-server=NUM)

[vtta]

aria2c defaults to a maximum of 16 connections per server, which is too small for downloading large files. This PR remove such limits so that one can easily saturate the network bandwidth when downloading.

Before:

 -x, --max-connection-per-server=NUM The maximum number of connections to one
                              server for each download.

                              Possible Values: 1-16
                              Default: 1
                              Tags: #basic, #http, #ftp

After:

 -x, --max-connection-per-server=NUM The maximum number of connections to one
                              server for each download.

                              Possible Values: 1-*
                              Default: 1
                              Tags: #basic, #http, #ftp

[abcfy2]

Thanks for the PR.

But at the moment I have no intention of merging unofficial patches. Because I'm concerned about the potential lack of maintenance of these patches, which could lead to unsuccessful patching of the code in the future.

Feel free to patch it in your fork.

Thank you all the same.