Update Gradle, Kotlin, and Gradle plug-in for Android

Trying to build/install this application in a new installation of Android Studio yielded:

> Unable to determine application id: com.android.tools.idea.run.ApkProvisionException: Error loading build artifacts from:<snip>\sms-matrix\app\build\outputs\apk\debug\output-metadata.json

This updates the versions of applications central to building the Android project to make it compatible. This does not (intentionally, at least) have any functional impact on the application at all.

I opted not to jump to Gradle 7.0 as it has just recently been released and increasing 1 major version is change enough for one PR.

build.gradle

@@ -1,14 +1,14 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
-    ext.kotlin_version = '1.3.10'
+    ext.kotlin_version = '1.4.20'
 
     repositories {
         google()
         jcenter()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.5.1'
+        classpath 'com.android.tools.build:gradle:4.1.3'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
         classpath "io.realm:realm-gradle-plugin:5.8.0"
 

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
-#Fri Oct 11 22:28:14 EEST 2019
+#Mon May 03 19:17:08 EDT 2021
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-5.4.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.8.3-all.zip