setup: add comment to remove dependency

Signed-off-by: Alessandro Comodi <acomodi@antmicro.com>

setup.py

diff --git a/setup.py b/setup.py
index d1388b5..61f4749 100644
--- a/setup.py
+++ b/setup.py
@@ -28,6 +28,8 @@
         'fasm',
         'intervaltree',
         'numpy',
+        # FIXME: remove dependency once https://github.com/SymbiFlow/prjxray/issues/1624
+        #        is fixed
         'pyjson5',
         'pyyaml',
         'simplejson',