software: Lock yosys to pre 0.48 relase.

The 0.48 release of yosys is dropping the ilang alias. We have to wait
for amaranth release with the appropriate fix to be released before we
can remove this constraint.

software/pyproject.toml

@@ -62,7 +62,7 @@ builtin-toolchain = [
   # the lowest that has features transitively required by Glasgow.
   "yowasp-runtime>=1.42",
   # Most versions of Yosys and nextpnr work; the minimum versions listed here are known good.
-  "yowasp-yosys>=0.31.0.13",
+  "yowasp-yosys>=0.31.0.13,<0.48",
   "yowasp-nextpnr-ice40>=0.1",
 ]