Convert barrier to MaD

I confirmed that without the model a test fails.

csharp/ql/lib/ext/System.Web.model.yml

@@ -1,4 +1,10 @@
 extensions:
+  - addsTo:
+      pack: codeql/csharp-all
+      extensible: barrierModel
+    data:
+      # The RawUrl property is considered to be safe for URL redirects
+      - ["System.Web", "HttpRequest", False, "get_RawUrl", "()", "", "ReturnValue", "url-redirection", "manual"]
   - addsTo:
       pack: codeql/csharp-all
       extensible: sinkModel

csharp/ql/lib/semmle/code/csharp/security/dataflow/UrlRedirectQuery.qll

@@ -189,16 +189,6 @@ class HostComparisonSanitizer extends Sanitizer {
   }
 }
 
-/**
- * A call to the getter of the RawUrl property, whose value is considered to be safe for URL
- * redirects.
- */
-class RawUrlSanitizer extends Sanitizer {
-  RawUrlSanitizer() {
-    this.getExpr() = any(SystemWebHttpRequestClass r).getRawUrlProperty().getGetter().getACall()
-  }
-}
-
 /**
  * A string concatenation expression, where the left hand side contains the character "?".
  *