Specify JDK toolchain directly

Specifying JDK toolchain in the java block lets us avoid specifying
same version again and again for different options while ensuring everything
is on the same version

Ref: https://developer.android.com/build/jdks#toolchain

Signed-off-by: Aayush Gupta <aayushgupta219@gmail.com>

app/build.gradle.kts

@@ -9,7 +9,6 @@
 
 import com.google.devtools.ksp.KspExperimental
 import java.util.Properties
-import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 
 plugins {
     alias(libs.plugins.android.application)
@@ -28,10 +27,14 @@ val lastCommitHash = providers.exec {
     commandLine("git", "rev-parse", "--short", "HEAD")
 }.standardOutput.asText.map { it.trim() }
 
+java {
+    toolchain {
+        languageVersion = JavaLanguageVersion.of(21)
+    }
+}
+
 kotlin {
-    jvmToolchain(21)
     compilerOptions {
-        jvmTarget = JvmTarget.JVM_21
         freeCompilerArgs.addAll(
             "-Xannotation-default-target=param-property"
         )
@@ -140,11 +143,6 @@ android {
         compose = true
     }
 
-    compileOptions {
-        sourceCompatibility = JavaVersion.VERSION_21
-        targetCompatibility = JavaVersion.VERSION_21
-    }
-
     lint {
         lintConfig = file("lint.xml")
     }