Remove the `art-gtest-valgrind32` testrunner configuration.

Test: n/a
Bug: 29282211
Change-Id: Ie041bb3cb65ef2688ce911e4faa02d05476cfb6d
diff --git a/test/testrunner/target_config.py b/test/testrunner/target_config.py
index 68efcaf..6310da6 100644
--- a/test/testrunner/target_config.py
+++ b/test/testrunner/target_config.py
@@ -265,14 +265,8 @@
             'ART_USE_READ_BARRIER' : 'false'
         }
     },
-    'art-gtest-valgrind32': {
-      # Disabled: Valgrind is no longer supported.
-      # Historical note: This was already disabled, as x86 valgrind did not understand SSE4.x
-      # 'make' : 'valgrind-test-art-host32',
-        'env': {
-            'ART_USE_READ_BARRIER' : 'false'
-        }
-    },
+    # TODO: Remove this configuration, when the ART Buildbot is no
+    # longer using it for 'host-x86_64-valgrind'.
     'art-gtest-valgrind64': {
       # Disabled: Valgrind is no longer supported.
       # 'make' : 'valgrind-test-art-host64',