Drop PR-reference from Argument-shape section header

Remove the "(PR B)" qualifier from the section header per the reviewer
request. Code should not reference other PRs in the stack — the section
header describes the tests' scope.

Signed-off-by: Eric Wei <mengwei.eric@gmail.com>

Author: mengweieric

integ-test/src/test/java/org/opensearch/sql/sql/VectorSearchIT.java

@@ -301,7 +301,7 @@ public void testExplainWithoutKnnPluginStillWorks() throws IOException {
     assertThat(explain, containsString("wrapper"));
   }
 
-  // ── Argument shape validation (PR B) ──────────────────────────────────
+  // ── Argument shape validation ─────────────────────────────────────────
 
   @Test
   public void testInvalidTableNameRejected() throws IOException {