[yugabyte#27526] Docdb: Test. Fix flakieness in PgMiniTestTracing.Tracing seen in tsan

Summary:
a0e6d55 refactored PgMiniTestTracing.Tracing to make it a parameterized
test, and in the process set the flag `enable_tracing=true`. Setting the flag to `true` is not necessary
and makes the test flaky in slow tests.

Slow tests (with enable_tracing set to true) may cause unrelated rpcs traces to get logged,
This makes the test flacky as the test expects that the latest trace dumped has to be a certain size.

Setting `enable_tracing` to `false` prevents the flakieness as only the rpcs originating from the
session in the test will log the traces.
Jira: DB-17087

Test Plan:
Jenkins: test regex: PgMiniTestTracing/PgMiniTestTracing.Tracing/*

yb_buid.sh  --cxx-test pgwrapper_pg_mini-test --gtest_filter PgMiniTestTracing/PgMiniTestTracing.Tracing/*

Reviewers: bkolagani, rthallam

Reviewed By: bkolagani

Subscribers: ybase, yql

Differential Revision: https://phorge.dev.yugabyte.com/D44598

Author: amitanandaiyer

src/yb/yql/pgwrapper/pg_mini-test.cc

@@ -553,7 +553,7 @@ TEST_F(PgMiniTest, Simple) {
 class PgMiniTestTracing : public PgMiniTest, public ::testing::WithParamInterface<bool> {
  protected:
   void SetUp() override {
-    ANNOTATE_UNPROTECTED_WRITE(FLAGS_enable_tracing) = true;
+    ANNOTATE_UNPROTECTED_WRITE(FLAGS_enable_tracing) = false;
     ANNOTATE_UNPROTECTED_WRITE(FLAGS_tracing_level) = 1;
     ANNOTATE_UNPROTECTED_WRITE(FLAGS_pg_client_use_shared_memory) = GetParam();
     PgMiniTest::SetUp();