Remove dead LoggerType class

This appears to have been factored into Loggers.qll but left lying around.

Author: smowton

csharp/ql/src/semmle/code/csharp/security/dataflow/LogForging.qll

@@ -48,13 +48,6 @@ module LogForging {
     HtmlSanitizer() { this.asExpr() instanceof HtmlSanitizedExpr }
   }
 
-  /**
-   * A logger type that extends from an ILogger type.
-   */
-  private class LoggerType extends RefType {
-    LoggerType() { getABaseType*().hasName("ILogger") }
-  }
-
   /**
    * An argument to a call to a method on a logger class.
    */