Modularized tests. Remove use of -Xuse-k2 argument in FP test

Use just language version to configure frontend, as -Xuse-k2 flag
is deprecated

^KT-56075

compiler/fir/modularized-tests/tests/org/jetbrains/kotlin/fir/FE1FullPipelineModularizedTest.kt

@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.fir
 
 import org.jetbrains.kotlin.cli.common.arguments.K2JVMCompilerArguments
+import org.jetbrains.kotlin.config.LanguageVersion
 
 /**
  * Language version to be used for K1 FP tests
@@ -31,6 +32,10 @@ class FE1FullPipelineModularizedTest : AbstractFullPipelineModularizedTest() {
             args.noStdlib = true
             args.noReflect = true
         }
+
+        require(LanguageVersion.fromVersionString(args.languageVersion)!! < LanguageVersion.KOTLIN_2_0) {
+            "Language version misconfiguration for K1 FP: ${args.languageVersion} >= 2.0"
+        }
     }
 
     fun testTotalKotlin() {

compiler/fir/modularized-tests/tests/org/jetbrains/kotlin/fir/FullPipelineModularizedTest.kt

@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.fir
 
 import org.jetbrains.kotlin.cli.common.arguments.K2JVMCompilerArguments
+import org.jetbrains.kotlin.config.LanguageVersion
 
 // This is used for API version configuration for both frontends
 // TODO: Deprecated and only used in old FP tests
@@ -17,7 +18,6 @@ internal val LANGUAGE_VERSION_K2: String = System.getProperty("fir.bench.languag
 class FullPipelineModularizedTest : AbstractFullPipelineModularizedTest() {
 
     override fun configureArguments(args: K2JVMCompilerArguments, moduleData: ModuleData) {
-        args.useK2 = true
         args.useIR = true
         args.languageVersion = LANGUAGE_VERSION_K2
 
@@ -34,6 +34,10 @@ class FullPipelineModularizedTest : AbstractFullPipelineModularizedTest() {
             args.noStdlib = true
             args.noReflect = true
         }
+
+        require(LanguageVersion.fromVersionString(args.languageVersion)!! >= LanguageVersion.KOTLIN_2_0) {
+            "Language version misconfiguration for K2 FP: ${args.languageVersion} < 2.0"
+        }
     }
 
     fun testTotalKotlin() {