Get rid of ToolsArtifacts builds

Pregel example project can build like any other. If we want to manage it
separately somehow, we should find a more meaningful way to do so.

Author: jjaderberg

examples/pregel-example/build.gradle

@@ -12,8 +12,6 @@ dependencies {
     annotationProcessor group: 'org.immutables',           name: 'builder',            version: ver.'immutables'
     annotationProcessor group: 'org.immutables',           name: 'value',              version: ver.'immutables'
 
-    api project(':proc-common')
-
     implementation project(':algo-common')
     implementation project(':annotations')
     implementation project(':config-api')
@@ -22,6 +20,7 @@ dependencies {
     implementation project(':memory-usage')
     implementation project(':neo4j-adapter')
     implementation project(':pregel')
+    implementation project(':proc-common')
     implementation project(':proc-pregel')
 
     compileOnly group: 'org.immutables', name: 'value-annotations', version: ver.'immutables'