Remove sljf4j-nop logger to avoid swallowing logs

[transducer]

Hi James,

With the slf4j-nop included, in projects requiring duct/module.web all logs are swallowed when used in combination with duct.logger.clojure, clojure.tools.logging and Logback.

The way to avoid that is by explicitly excluding this dependency. E.g., in project.clj:

;; Exclusion needed to prevent slf4j 'no operation' logging to
;; take precedence over logback logging
[duct/module.web "0.7.0" :exclusions [org.slf4j/slf4j-nop]]
[org.clojure/tools.logging "1.0.0"]
[duct/logger.clojure "0.1.1"]
[ch.qos.logback/logback-classic "1.2.3" :exclusions [org.slf4j/slf4j-api]]
[org.slf4j/slf4j-api "1.7.30"]
[org.slf4j/jul-to-slf4j "1.7.30"]
[org.slf4j/jcl-over-slf4j "1.7.30"]
[org.slf4j/log4j-over-slf4j "1.7.30"]

I don't know what the reason was to add slf4j-nop (maybe it is to remove logging of Jetty or other type of :duct.server/http), so maybe this PR needs some changes to re-add that behaviour if so desired.

Kind regards,
Erwin