vuln-fix: Use HTTPS instead of HTTP to resolve dependencies

This fixes a security vulnerability in this project where the `build.gradle`
files were configuring Gradle to resolve dependencies over HTTP instead of
HTTPS.

Weakness: CWE-829: Inclusion of Functionality from Untrusted Control Sphere
Severity: High
CVSSS: 8.1
Detection: OpenRewrite

Reported-by: Jonathan Leitschuh <Jonathan.Leitschuh@gmail.com>
Signed-off-by: Jonathan Leitschuh <Jonathan.Leitschuh@gmail.com>

Bug-tracker: JLLeitschuh/security-research#9

Co-authored-by: Moderne <team@moderne.io>

build.gradle

@@ -1,7 +1,7 @@
 buildscript {
   repositories {
     jcenter()
-    maven { url "http://repo.spring.io/libs-release" }
+    maven { url "https://repo.spring.io/libs-release" }
     mavenCentral()
   }
 }