Remove LANGUAGE_VERSION from non-coroutine codegen tests

Most of these tests used this directive as a way to opt in to a new
language feature, and most of those features are already stable for a
long time, so no opt-in is needed. Some other tests used the directive
to opt out from a language feature, replace those by the `LANGUAGE`
directive. One test used the directive to test behavior that actually
depended on the API version; use `API_VERSION` directive there instead.

compiler/testData/codegen/box/operatorConventions/percentAsModOnBigIntegerWithoutRem.kt

@@ -1,6 +1,6 @@
+// !LANGUAGE: -ProhibitOperatorMod
+// !API_VERSION: 1.0
 // TARGET_BACKEND: JVM
-
-// LANGUAGE_VERSION: 1.0
 // FULL_JDK
 
 import java.math.BigInteger
@@ -8,4 +8,4 @@ import java.math.BigInteger
 fun box(): String {
     val m = BigInteger.valueOf(-2) % BigInteger.valueOf(3)
     return if (m != BigInteger.valueOf(1)) "Fail: BigInteger(-2) mod BigInteger(3) == $m" else "OK"
-}
+}