QL: show recommendation queries by default, and remove the MissingQLDoc query

ql/ql/src/codeql-suites/ql-code-scanning.qls

@@ -12,6 +12,7 @@
     problem.severity:
     - error
     - warning
+    - recommendation
 - exclude:
     deprecated: //
 - exclude:

ql/ql/src/queries/style/docs/MissingQLDoc.ql

@@ -1,25 +0,0 @@
-/**
- * @name Missing QLDoc.
- * @description Library classes should have QLDoc.
- * @kind problem
- * @problem.severity recommendation
- * @id ql/missing-qldoc
- * @tags maintainability
- * @precision high
- */
-
-import ql
-
-from File f, Class c
-where
-  f = c.getLocation().getFile() and
-  not exists(c.getQLDoc()) and // no QLDoc
-  f.getExtension() = "qll" and // in a library
-  not c.isPrivate() and // class is public
-  not exists(Module m |
-    m.getAMember*() = c and
-    m.isPrivate() // modules containing the class are public
-  ) and
-  not exists(c.getAliasType()) and // class is not just an alias
-  not f.getParentContainer*().getBaseName().toLowerCase() = ["internal", "experimental", "test"] // exclusions
-select c, "This library class should have QLDoc."