Remove fuzz.go

[dolmen]

fuzz.go added in #1097 is now obsolete:

• it was written for go-fuzz but should be at least ported to the Go 1.18 fuzzing framework
• error handling/reporting is almost inexistant
• running the fuzzer is dangerous as it might connect to random machines on the Internet because the fuzzing process might generate those IP/port (so just porting would be a bad idea)
• it fuzzes DSN which is now redundant with fuzzing I have just proposed in Add fuzz test for ParseDSN / FormatDSN roundtrip #1444
• the fuzzer was written for oss-fuzz, but I haven't found the matching project in https://github.com/google/oss-fuzz/tree/master/projects
• according to oss-fuzz documentation the project should have a cifuzz.yml, but we haven't one

So if we want to participate to oss-fuzz a different fuzzer should be implemented (#1444 is a good start) and the project must be registered.

As is fuzz.go is just useless and can be deleted.