[2036] Add a note about not using obj: lines in suppressions

src/valgrind-suppressions

@@ -3,5 +3,9 @@
 # that we want to revisit in the future, use
 # valgrind-suppressions.revisit.
 #
+# Don't add any "obj:" lines in suppressions as these are likely
+# site-specific. Use "..." instead to match these. Look at the other
+# suppressions as examples.
+#
 # In case you want to make sense of the following symbols, demangle them
 # with a command like: c++filt < valgrind-suppressions

src/valgrind-suppressions.revisit

@@ -2,6 +2,10 @@
 # into this file. For permanent suppressions that we don't want to look
 # at again, use valgrind-suppressions.
 #
+# Don't add any "obj:" lines in suppressions as these are likely
+# site-specific. Use "..." instead to match these. Look at the other
+# suppressions as examples.
+#
 # In case you want to make sense of the following symbols, demangle them
 # with a command like: c++filt < valgrind-suppressions.revisit