[SPARK-24544][SQL][FOLLOWUP] Remove a wrong warning on Hive fallback lookup

## What changes were proposed in this pull request?

This PR is a follow-up of #21790 which causes a regression to show misleading warnings always at first invocation for all Hive function. Hive fallback lookup should not be warned. It's a normal process in function lookups.

**CURRENT (Showing `NoSuchFunctionException` and working)**
```scala
scala> sql("select histogram_numeric(a,2) from values(1) T(a)").show
19/06/02 22:02:10 WARN HiveSessionCatalog: Encountered a failure during looking up
function: org.apache.spark.sql.catalyst.analysis.NoSuchFunctionException:
Undefined function: 'histogram_numeric'. This function is neither a registered temporary
function nor a permanent function registered in the database 'default'.;
  at org.apache.spark.sql.catalyst.catalog.SessionCatalog.failFunctionLookup(SessionCatalog.scala:1234)
  at org.apache.spark.sql.catalyst.catalog.SessionCatalog.lookupFunction(SessionCatalog.scala:1302)
...
+------------------------+
|histogram_numeric( a, 2)|
+------------------------+
|            [[1.0, 1.0]]|
+------------------------+
```

## How was this patch tested?

Manually execute the above query.

Closes #24773 from dongjoon-hyun/SPARK-24544.

Authored-by: Dongjoon Hyun <dhyun@apple.com>
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>

Author: dongjoon-hyun

sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveSessionCatalog.scala

@@ -142,8 +142,6 @@ private[sql] class HiveSessionCatalog(
           // let's try to load it as a Hive's built-in function.
           // Hive is case insensitive.
           val functionName = funcName.unquotedString.toLowerCase(Locale.ROOT)
-          logWarning("Encountered a failure during looking up function:" +
-            s" ${Utils.exceptionString(error)}")
           if (!hiveFunctions.contains(functionName)) {
             failFunctionLookup(funcName, Some(error))
           }