chore: default to scala3 (#84)

also: drop maven and gradle builds, now available through downloadable zip in akka-grpc docs.

.github/workflows/ci.yml

@@ -35,20 +35,13 @@ jobs:
         # v6.4.5
         uses: coursier/cache-action@1ff273bff02a8787bc9f1877d347948af647956d
 
-      - name: sbt test
-        run: sbt test
-
-      - name: sbt Scala 3
+      - name: sbt 2.13 test
         run: |-
-          sbt new file://$PWD --name=hello-world --scala_version=3.3.1 --force && pushd hello-world &&  sbt test
+          sbt new file://$PWD --name=hello-world213 --scala_version=2.13.14 --force && pushd hello-world213 &&  sbt test
 
-      - name: Maven
-        run: |-
-          sbt new file://$PWD --name=hello-world-grpc --force && pushd hello-world-grpc &&  mvn test
-
-      - name: Gradle
+      - name: sbt Scala 3
         run: |-
-          sbt new file://$PWD --name=hello-world-grpc --force && pushd hello-world-grpc &&  ./gradlew --console=plain build -i --no-daemon
+          sbt new file://$PWD --name=hello-world3 --scala_version=3.3.3 --force && pushd hello-world3 &&  sbt test
 
       - name: Email on failure
         if: ${{ failure() }}

src/main/g8/default.properties

@@ -3,6 +3,5 @@ description = Akka gRPC is a toolkit for building streaming gRPC servers and cli
 akka_grpc_version=2.4.3
 akka_version=2.9.3
 sbt_version=maven(org.scala-sbt, sbt, stable)
-scala_major_version=2.13
-scala_version=2.13.14
+scala_version=3.3.3
 verbatim=*.scala *.conf *.proto *.pem *.key gradlew gradlew.bat gradle-wrapper.properties gradle-wrapper.jar