[GLUTEN-12157][VL] Drop ln registration — prestosql::LnFunction has different null semantics

Author: brijrajk

backends-velox/src/test/scala/org/apache/gluten/functions/MathFunctionsValidateSuite.scala

@@ -256,12 +256,6 @@ class MathFunctionsValidateSuite extends FunctionsValidateSuite {
     }
   }
 
-  test("ln") {
-    runQueryAndCompare("SELECT ln(l_orderkey) from lineitem limit 1") {
-      checkGlutenPlan[ProjectExecTransformer]
-    }
-  }
-
   test("log") {
     runQueryAndCompare("SELECT log(10, l_orderkey) from lineitem limit 1") {
       checkGlutenPlan[ProjectExecTransformer]

cpp/velox/operators/functions/RegistrationAllFunctions.cc

@@ -80,7 +80,6 @@ void registerFunctionOverwrite() {
   // Register math functions that are present in the prestosql implementation
   // but not yet in the sparksql registry. These are semantically identical
   // to Spark's behavior for the same names.
-  velox::registerFunction<velox::functions::LnFunction, double, double>({"ln"});
   velox::registerFunction<velox::functions::RadiansFunction, double, double>({"radians"});
   velox::registerFunction<velox::functions::SinFunction, double, double>({"sin"});
   velox::registerFunction<velox::functions::TanFunction, double, double>({"tan"});