updating min SDK version to 23, Marshmallow Android 6

app/build.gradle

@@ -15,7 +15,7 @@ android {
 
     defaultConfig {
         applicationId "com.simplemobiletools.contacts.pro"
-        minSdkVersion 21
+        minSdkVersion 23
         targetSdkVersion 29
         versionCode 60
         versionName "6.9.0"

app/src/main/kotlin/com/simplemobiletools/contacts/pro/activities/DialerActivity.kt

@@ -1,10 +1,8 @@
 package com.simplemobiletools.contacts.pro.activities
 
 import android.annotation.SuppressLint
-import android.annotation.TargetApi
 import android.content.Intent
 import android.net.Uri
-import android.os.Build
 import android.os.Bundle
 import android.telecom.PhoneAccount
 import android.telecom.TelecomManager
@@ -16,7 +14,6 @@ import com.simplemobiletools.commons.extensions.toast
 import com.simplemobiletools.commons.helpers.REQUEST_CODE_SET_DEFAULT_DIALER
 import com.simplemobiletools.contacts.pro.R
 
-@TargetApi(Build.VERSION_CODES.M)
 class DialerActivity : SimpleActivity() {
     private var callNumber: Uri? = null
 

app/src/main/kotlin/com/simplemobiletools/contacts/pro/services/CallService.kt

@@ -1,14 +1,11 @@
 package com.simplemobiletools.contacts.pro.services
 
 import android.content.Intent
-import android.os.Build
 import android.telecom.Call
 import android.telecom.InCallService
-import androidx.annotation.RequiresApi
 import com.simplemobiletools.contacts.pro.activities.CallActivity
 import com.simplemobiletools.contacts.pro.helpers.CallManager
 
-@RequiresApi(Build.VERSION_CODES.M)
 class CallService : InCallService() {
     override fun onCallAdded(call: Call) {
         super.onCallAdded(call)