Remove obsolete compiler flag -Xuse-ir

compiler/incremental-compilation-impl/test/org/jetbrains/kotlin/incremental/AbstractIncrementalFirICLightTreeJvmCompilerRunnerTest.kt

@@ -14,7 +14,6 @@ abstract class AbstractIncrementalFirICLightTreeJvmCompilerRunnerTest : Abstract
         super.createCompilerArguments(destinationDir, testDir).apply {
             useK2 = true
             languageVersion = "2.0"
-            useIR = true
             useFirIC = true
             useFirLT = true
         }

compiler/incremental-compilation-impl/test/org/jetbrains/kotlin/incremental/AbstractIncrementalFirJvmCompilerRunnerTest.kt

@@ -25,7 +25,6 @@ abstract class AbstractIncrementalFirJvmCompilerRunnerTest : AbstractIncremental
         super.createCompilerArguments(destinationDir, testDir).apply {
             useK2 = true
             languageVersion = "2.0"
-            useIR = true
         }
 
     override val buildLogFinder: BuildLogFinder

compiler/incremental-compilation-impl/test/org/jetbrains/kotlin/incremental/AbstractIncrementalFirLightTreeJvmCompilerRunnerTest.kt

@@ -14,7 +14,6 @@ abstract class AbstractIncrementalFirLightTreeJvmCompilerRunnerTest : AbstractIn
         super.createCompilerArguments(destinationDir, testDir).apply {
             useK2 = true
             languageVersion = "2.0"
-            useIR = true
             useFirIC = false
             useFirLT = true
         }