Lower system memory requirements for tests to support ci runners <4GiB

diff --git a/crates/arti/src/arti-example-config.toml b/crates/arti/src/arti-example-config.toml
index 5b53cb2f1..691f0fe7f 100644
--- a/crates/arti/src/arti-example-config.toml
+++ b/crates/arti/src/arti-example-config.toml
@@ -549,7 +549,7 @@
 # If `system.memory.low_water` is given as an explicit value,
 # `system.memory.max` must also be given as an explicit value.
 #
-#    memory.max = "8 GiB"
+#    memory.max = "3 GiB"
 
 # Low-water mark for tracked memory:
 # When reclaiming memory, we stop when we reach this amount.
@@ -558,7 +558,7 @@
 # assumed that the value used for "auto" will remain stable across different
 # versions of arti.
 #
-#    memory.low_water = "6 GiB"
+#    memory.low_water = "2.25 GiB"
 
 ##### ONION SERVICES
 #
