Remove partial javastream proto support

javastream proto is rarely used and tricky to support directly
in java because it depends on an extra host tool.  It can be
supported with a genrule, so just remove the partial built-in
support.

Test: m checkbuild
Change-Id: Iffe75e7040cb889ca17fdd85ef3e8e64fc3aa9e9
diff --git a/java/proto.go b/java/proto.go
index eeb5124..17f02a3 100644
--- a/java/proto.go
+++ b/java/proto.go
@@ -63,10 +63,6 @@
 		ctx.AddDependency(ctx.Module(), staticLibTag, "libprotobuf-java-micro")
 	case "nano":
 		ctx.AddDependency(ctx.Module(), staticLibTag, "libprotobuf-java-nano")
-	case "stream":
-		// TODO(ccross): add dependency on protoc-gen-java-stream binary
-		ctx.PropertyErrorf("proto.type", `"stream" not supported yet`)
-		// No library for stream protobufs
 	case "lite", "":
 		ctx.AddDependency(ctx.Module(), staticLibTag, "libprotobuf-java-lite")
 	case "full":
@@ -87,8 +83,6 @@
 		flags.protoOutFlag = "--javamicro_out"
 	case "nano":
 		flags.protoOutFlag = "--javanano_out"
-	case "stream":
-		flags.protoOutFlag = "--javastream_out"
 	case "lite", "full", "":
 		flags.protoOutFlag = "--java_out"
 	default: