Revert "conf/requirements: temporarily pin f4pga"

This reverts commit 9e82b01.

Author: umarcor

conf/requirements.txt

@@ -14,4 +14,4 @@ termcolor
 terminaltables
 yapf==0.31.0
 git+https://github.com/SymbiFlow/edalize.git@symbiflow_update#egg=edalize
-https://github.com/chipsalliance/f4pga/archive/de9ed1f3dba34d641c354bdb070232887254b142.zip#subdirectory=f4pga
+https://github.com/chipsalliance/f4pga/archive/main.zip#subdirectory=f4pga