Use API_VERSION instead of LANGUAGE_VERSION in IEEE754 tests

See `ExpressionCodegen.genEqualsForExpressionsPreferIeee754Arithmetic`:
the behavior here actually depends on the API version, not any language
feature

compiler/testData/codegen/bytecodeText/ieee754/nullableDoubleEquals10.kt

@@ -1,4 +1,4 @@
-// LANGUAGE_VERSION: 1.0
+// !API_VERSION: 1.0
 
 fun myEquals(a: Double?, b: Double?) = a == b
 

compiler/testData/codegen/bytecodeText/ieee754/nullableDoubleNotEquals10.kt

@@ -1,4 +1,5 @@
-// LANGUAGE_VERSION: 1.0
+// !API_VERSION: 1.0
+
 fun myNotEquals(a: Double?, b: Double?) = a != b
 
 fun myNotEquals1(a: Double?, b: Double) = a != b

compiler/testData/codegen/bytecodeText/ieee754/nullableFloatEquals10.kt

@@ -1,4 +1,5 @@
-// LANGUAGE_VERSION: 1.0
+// !API_VERSION: 1.0
+
 fun myEquals(a: Float?, b: Float?) = a == b
 
 fun myEquals1(a: Float?, b: Float) = a == b

compiler/testData/codegen/bytecodeText/ieee754/nullableFloatNotEquals10.kt

@@ -1,4 +1,5 @@
-// LANGUAGE_VERSION: 1.0
+// !API_VERSION: 1.0
+
 fun myNotEquals(a: Float?, b: Float?) = a != b
 
 fun myNotEquals1(a: Float?, b: Float) = a != b

compiler/testData/codegen/bytecodeText/ieee754/smartCastsForDouble10.kt

@@ -1,4 +1,4 @@
-// LANGUAGE_VERSION: 1.0
+// !API_VERSION: 1.0
 
 fun equals5(a: Any?, b: Any?) = if (a is Double && b is Double?) a == b else null!!
 
@@ -20,4 +20,4 @@ fun box(): String {
 }
 
 // 3 areEqual \(Ljava/lang/Object;Ljava/lang/Object;\)Z
-// 3 areEqual
+// 3 areEqual

compiler/testData/codegen/bytecodeText/ieee754/smartCastsForFloat10.kt

@@ -1,4 +1,4 @@
-// LANGUAGE_VERSION: 1.0
+// !API_VERSION: 1.0
 
 fun equals5(a: Any?, b: Any?) = if (a is Float && b is Float?) a == b else null!!
 
@@ -20,4 +20,4 @@ fun box(): String {
 }
 
 // 3 areEqual \(Ljava/lang/Object;Ljava/lang/Object;\)Z
-// 3 areEqual
+// 3 areEqual

compiler/testData/codegen/bytecodeText/ieee754/when10.kt

@@ -1,4 +1,5 @@
-// LANGUAGE_VERSION: 1.0
+// !API_VERSION: 1.0
+
 fun box(): String {
     val plusZero: Any = 0.0
     val minusZero: Any = -0.0
@@ -29,4 +30,4 @@ fun box(): String {
 }
 
 // 4 areEqual \(Ljava/lang/Object;Ljava/lang/Object;\)Z
-// 4 areEqual
+// 4 areEqual

compiler/testData/codegen/bytecodeText/ieee754/whenNullableSmartCast10.kt

@@ -1,4 +1,5 @@
-// LANGUAGE_VERSION: 1.0
+// !API_VERSION: 1.0
+
 fun box(): String {
     val nullValue: Any? = null
     val nullDouble: Double? = null
@@ -26,5 +27,6 @@ fun box(): String {
     }
     return "OK"
 }
+
 // 4 areEqual \(Ljava/lang/Object;Ljava/lang/Object;\)Z
 // 4 areEqual