Add back inputs on processResources

I kinda thought that Gradle would be smart enough to know that these
were input (given they're passed to expand), but apparently not :/.

projects/forge/build.gradle.kts

@@ -190,6 +190,9 @@ dependencies {
 // Compile tasks
 
 tasks.processResources {
+    inputs.property("modVersion", modVersion)
+    inputs.property("forgeVersion", libs.versions.forge)
+
     var props = mapOf(
         "forgeVersion" to libs.versions.forge.get(),
         "file" to mapOf("jarVersion" to modVersion),