Revert "feat: Enable leader aware routing by default" (#2547)

Reverts #2538

Author: rajatbhatta

google-cloud-spanner/src/main/java/com/google/cloud/spanner/SpannerOptions.java

@@ -700,7 +700,7 @@ public static class Builder
     private CloseableExecutorProvider asyncExecutorProvider;
     private String compressorName;
     private String emulatorHost = System.getenv("SPANNER_EMULATOR_HOST");
-    private boolean leaderAwareRoutingEnabled = true;
+    private boolean leaderAwareRoutingEnabled = false;
 
     private Builder() {
       // Manually set retry and polling settings that work.

google-cloud-spanner/src/test/java/com/google/cloud/spanner/SpannerOptionsTest.java

@@ -680,7 +680,8 @@ public void testCompressorName() {
 
   @Test
   public void testLeaderAwareRoutingEnablement() {
-    assertTrue(SpannerOptions.newBuilder().setProjectId("p").build().isLeaderAwareRoutingEnabled());
+    assertFalse(
+        SpannerOptions.newBuilder().setProjectId("p").build().isLeaderAwareRoutingEnabled());
     assertTrue(
         SpannerOptions.newBuilder()
             .setProjectId("p")