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/fabric/build.gradle.kts

@@ -220,6 +220,8 @@ loom {
 }
 
 tasks.processResources {
+    inputs.property("modVersion", modVersion)
+
     var props = mapOf("version" to modVersion)
 
     filesMatching("fabric.mod.json") { expand(props) }