chore(isthmus): debug log missing Calcite mapping (#516)

There is an info level log in FunctionConverter for every every Calcite
operator for which there is no direct Substrait mapping. This message
makes the logs extremely busy and provides no value to end users. This
change reclassifies the message as debug log.

Signed-off-by: Mark S. Lewis <[email protected]>

Author: bestbeforetoday

isthmus/src/main/java/io/substrait/isthmus/expression/FunctionConverter.java

@@ -90,7 +90,7 @@ public FunctionConverter(
     for (String key : alm.keySet()) {
       Collection<Sig> sigs = calciteOperators.get(key);
       if (sigs.isEmpty()) {
-        LOGGER.atInfo().log("No binding for function: {}", key);
+        LOGGER.atDebug().log("No binding for function: {}", key);
       }
 
       for (Sig sig : sigs) {