build: restore legacy mod build compatibility

Normalize the legacy build definition used for the Java 8 Uranium full-mod deployment.

build.gradle

@@ -1,3 +1,6 @@
 plugins {
     id 'com.gtnewhorizons.gtnhconvention'
 }
+
+version = providers.gradleProperty('modVersion').get()
+ext.modVersion = version

gradle.properties

@@ -3,7 +3,8 @@ gtnh.settings.blowdryerTag = 0.2.0
 modName = SlashBlade Kirisaya
 modId = flammpfeil.slashblade.kirisaya
 modGroup = mods.flammpfeil.slashblade.kirisaya
-modVersion = 1.0.0
+modVersion = r1
+gtnh.modules.gitVersion = false
 useModGroupForPublishing = false
 autoUpdateBuildScript = false