configure: Bump minimal boot GHC version to 9.4

(cherry picked from commit d3ffdaf9)

configure.ac

@@ -231,7 +231,7 @@ if test "$WithGhc" = ""
 then
     AC_MSG_ERROR([GHC is required.])
 fi
-MinBootGhcVersion="9.2"
+MinBootGhcVersion="9.4"
 FP_COMPARE_VERSIONS([$GhcVersion],[-lt],[$MinBootGhcVersion],
     [AC_MSG_ERROR([GHC version $MinBootGhcVersion or later is required to compile GHC.])])