fpga-shells: bump to fix timing closure

diff --git a/fpga-shells b/fpga-shells
index 17e13a3a5078e76483f7c30a3b513507f0c9ebd6..1dda5255786d5ec5d35db8bff037eb0fbd2c9984 160000 (submodule)
--- a/fpga-shells
+++ b/fpga-shells
@@ -1 +1 @@
-Subproject commit 17e13a3a5078e76483f7c30a3b513507f0c9ebd6
+Subproject commit 1dda5255786d5ec5d35db8bff037eb0fbd2c9984