Fix small issues with the tutorial docs

[ssanj]

Fixed a couple of small discrepancies in the docs:

1 The diagnostic error states that this should be the error:

===========> Unreported <===========
test/NoLiteralArgumentsConfig.scala:16:20: error
  complete("done") // assert: NoLiteralArguments
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

but given the config and code provided:

/*
rule = NoLiteralArguments
NoLiteralArguments.disabledLiterals = [
  Int
  Boolean
]
 */
package test

class NoLiteralArgumentsConfig {
  def complete(message: String): Unit = ()
  def complete(count: Int): Unit = ()
  def complete(isSuccess: Boolean): Unit = ()
  complete("done") // ok, no error message
  complete(42) // assert: NoLiteralArguments
  complete(true) // assert: NoLiteralArguments
}

complete("done") should not report a lint error. (it also has the // ok, no error message comment)

Updated to report complete(42) as the error.

2. NoLiteralArgumentsConfig#isDisabled is defined with a parameter named literal but that parameter is used as lit:

  def isDisabled(literal: Lit): Boolean = {
    val kind = lit.productPrefix.stripPrefix("Lit.") //should be literal.productPrefix or literal should be renamed to 'lit'
    disabledLiterals.contains(kind)
  }

Renamed literal: Lit -> lit: Lit as it coincides with the scalafix-named-literal-arguments on master

[bjaglin]

Thanks @ssanj !