fix unused it

Author: koperagen

core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/testSets/person/DataFrameTests.kt

@@ -552,7 +552,7 @@ class DataFrameTests : BaseTest() {
 
     @Test
     fun `drop nulls 1`() {
-        fun AnyFrame.check() = rows().forEach { get("weight") shouldNotBe null }
+        fun AnyFrame.check() = rows().forEach { it["weight"] shouldNotBe null }
 
         typed.dropNulls(typed.weight).check()
         typed.dropNulls { weight }.check()