test: Update memory threshold to account for instrumentation

Updates memory threshold to account for instrumentation.

Signed-off-by: Jonathan Woollett-Light <jcawl@amazon.co.uk>

Author: Jonathan Woollett-Light

tests/host_tools/memory.py

@@ -26,7 +26,7 @@ class MemoryMonitor(Thread):
     VMM memory usage.
     """
 
-    MEMORY_THRESHOLD = 5 * 1024
+    MEMORY_THRESHOLD = 6 * 1024
     MEMORY_SAMPLE_TIMEOUT_S = 0.05
     X86_MEMORY_GAP_START = 3407872