java.starlark.net: delete StarlarkBuiltin.namespace() bool

All it does it append a suffix to str(x), which adds very
marginal value (and sometimes subtracts---see the test).

Apropos of https://github.com/google/starlark-go\
/issues/274.

PiperOrigin-RevId: 315606558
diff --git a/src/test/java/com/google/devtools/build/lib/skylark/StarlarkRuleClassFunctionsTest.java b/src/test/java/com/google/devtools/build/lib/skylark/StarlarkRuleClassFunctionsTest.java
index 089115e..ea1d36e 100644
--- a/src/test/java/com/google/devtools/build/lib/skylark/StarlarkRuleClassFunctionsTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skylark/StarlarkRuleClassFunctionsTest.java
@@ -695,9 +695,7 @@
   @Test
   public void testNoAttrLicense() throws Exception {
     EvalException expected = assertThrows(EvalException.class, () -> ev.eval("attr.license()"));
-    assertThat(expected)
-        .hasMessageThat()
-        .contains("'attr (a language module)' value has no field or method 'license'");
+    assertThat(expected).hasMessageThat().contains("'attr' value has no field or method 'license'");
   }
 
   @Test