Ruby: Remove redundant predicate

The existing barrier guard machinery recognises guards such as `if x and y`,
so there's no need to explicitly model them.

Author: hmac

ruby/ql/lib/codeql/ruby/dataflow/BarrierGuards.qll

@@ -35,8 +35,6 @@ private predicate stringConstCompare(CfgNodes::AstCfgNode guard, CfgNode testedN
     stringConstCompareOr(guard, def, branch) and
     stringConstCompare(g.getLeftOperand(), testedNode, _)
   )
-  or
-  stringConstCompareAnd(guard, testedNode, branch)
 }
 
 /**
@@ -57,23 +55,6 @@ private predicate stringConstCompareOr(
   )
 }
 
-/**
- * Holds if `guard` is an `and` expression containing a string comparison guard in either operand.
- * For example:
- *
- * ```rb
- * x == "foo" and other_condition()
- * other_condition() and x == "foo"
- * ```
- */
-private predicate stringConstCompareAnd(
-  CfgNodes::ExprNodes::BinaryOperationCfgNode guard, CfgNode testedNode, boolean branch
-) {
-  guard.getExpr() instanceof LogicalAndExpr and
-  branch = true and
-  stringConstCompare(guard.getAnOperand(), testedNode, branch)
-}
-
 /**
  * A validation of value by comparing with a constant string value, for example
  * in: