Verbose error log: URL query contains semicolon

[jbspeakr]

Describe the bug
Skipper does not support parsing of URL queries that contain semicolon, but logs an error if clients send semicolons. Logged errors should be actionable, which in this context is not the case since this is something the client does. It's not an error from Skipper's perspective.

Expected behavior
Log level of info would potentially (if a log message is actually required) make more sense in this case.

Observed behavior
with Skipper v0.13.185
time="2022-03-18T09:20:32Z" level=error msg="http: URL query contains semicolon, which is no longer a supported separator; parts of the query may be stripped when parsed; see golang.org/issue/25192\n"

[AlexanderYastrebov]

golang/go#25192 mentions two others golang/go#49399 and golang/go#50034
To mute the log message (if we decide so) the machinery introduced by #1904 can be used.