chore: change default threshold in fetch githubrepos

[MaineK00n]

What did you implement:

Change the (star, fork) threshold used in the fetch githubrepos command from (5, 5) to (3, 0).

Type of change

Please delete options that are not relevant.

• [x] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

// upstream/master
$ go-exploitdb fetch githubrepos --threshold-stars 3 --threshold-forks 0
INFO[08-12|12:20:47] Fetching GitHub Repos Exploit 
INFO[08-12|12:20:50] GitHub Repos Exploit                     count=2127
INFO[08-12|12:20:50] Insert Exploit into go-exploitdb.        db=sqlite3
INFO[08-12|12:20:50] Inserting 2127 Exploits 
2127 / 2127 [-----------------------------------------------------------------------------] 100.00% ? p/s
INFO[08-12|12:20:50] No CveID Exploit Count                   count=0
INFO[08-12|12:20:50] CveID Exploit Count                      count=2127

// PR
$ go-exploitdb fetch githubrepos
INFO[08-12|12:21:22] Fetching GitHub Repos Exploit 
INFO[08-12|12:21:25] GitHub Repos Exploit                     count=2127
INFO[08-12|12:21:25] Insert Exploit into go-exploitdb.        db=sqlite3
INFO[08-12|12:21:25] Inserting 2127 Exploits 
2127 / 2127 [-----------------------------------------------------------------------------] 100.00% ? p/s
INFO[08-12|12:21:25] No CveID Exploit Count                   count=0
INFO[08-12|12:21:25] CveID Exploit Count                      count=2127

Checklist:

You don't have to satisfy all of the following.

• [ ] Write tests
• [ ] Write documentation
• [x] Check that there aren't other open pull requests for the same issue/feature
• [x] Format your source code by make fmt
• [x] Pass the test by make test
• [x] Provide verification config / commands
• [x] Enable "Allow edits from maintainers" for this PR
• [x] Update the messages below

Is this ready for review?: YES

Reference