cleanup: revert unrelated change

Resolves:
- https://github.com/apache/iceberg/pull/8971/files/24e61436f3d6f696b4ddce80b75523a5db90fb5c?show-viewed-files=true&file-filters%5B%5D=#r1381238654

Author: jacobmarble

api/src/main/java/org/apache/iceberg/transforms/PartitionSpecVisitor.java

@@ -121,13 +121,24 @@ static <R> R visit(Schema schema, PartitionField field, PartitionSpecVisitor<R>
     } else if (transform instanceof Truncate) {
       int width = ((Truncate<?>) transform).width();
       return visitor.truncate(field.fieldId(), sourceName, field.sourceId(), width);
-    } else if ("year".equalsIgnoreCase(transform.toString())) {
+    } else if (transform == Dates.YEAR
+        || transform == Timestamps.YEAR_FROM_MICROS
+        || transform == Timestamps.YEAR_FROM_NANOS
+        || transform instanceof Years) {
       return visitor.year(field.fieldId(), sourceName, field.sourceId());
-    } else if ("month".equalsIgnoreCase(transform.toString())) {
+    } else if (transform == Dates.MONTH
+        || transform == Timestamps.MONTH_FROM_MICROS
+        || transform == Timestamps.MONTH_FROM_NANOS
+        || transform instanceof Months) {
       return visitor.month(field.fieldId(), sourceName, field.sourceId());
-    } else if ("day".equalsIgnoreCase(transform.toString())) {
+    } else if (transform == Dates.DAY
+        || transform == Timestamps.DAY_FROM_MICROS
+        || transform == Timestamps.DAY_FROM_NANOS
+        || transform instanceof Days) {
       return visitor.day(field.fieldId(), sourceName, field.sourceId());
-    } else if ("hour".equalsIgnoreCase(transform.toString())) {
+    } else if (transform == Timestamps.HOUR_FROM_MICROS
+        || transform == Timestamps.HOUR_FROM_NANOS
+        || transform instanceof Hours) {
       return visitor.hour(field.fieldId(), sourceName, field.sourceId());
     } else if (transform instanceof VoidTransform) {
       return visitor.alwaysNull(field.fieldId(), sourceName, field.sourceId());