Don't treat logrus' WithContext method as a logging function

This isn't output by the default formatters (though a custom formatter could potentially output things stored in it)

Author: smowton

go/ql/lib/semmle/go/frameworks/Logrus.qll

@@ -16,7 +16,7 @@ module Logrus {
 
   bindingset[result]
   private string getAnEntryUpdatingMethodName() {
-    result.regexpMatch("With(Context|Error|Fields?|Time)")
+    result.regexpMatch("With(Error|Fields?|Time)")
   }
 
   private class LogFunction extends Function {

go/ql/test/library-tests/semmle/go/concepts/LoggerCall/logrus.go

@@ -18,7 +18,7 @@ func logrusCalls() {
 	var fields logrus.Fields = nil
 	var fn logrus.LogFunction = nil
 	var ctx context.Context
-	tmp := logrus.WithContext(ctx)  // $ logger=ctx
+	tmp := logrus.WithContext(ctx)  // ctx isn't output, so no match here
 	tmp.Debugf(fmt, text)           // $ logger=fmt logger=text
 	tmp = logrus.WithError(err)     // $ logger=err
 	tmp.Warn(text)                  // $ logger=text