Disable test sharding for rde package

The tests in this package are failing for reasons likely related to resource consumption. Sharding an expensive test within a single test runner is probably causing more harm than good, so run this test in a single shard.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=141766295

javatests/google/registry/rde/BUILD

@@ -54,7 +54,6 @@ java_library(
 GenTestRules(
     name = "GeneratedTestRules",
     default_test_size = "medium",
-    shard_count = 4,
     test_files = glob(["*Test.java"]),
     deps = [":rde"],
 )