remove tests from passlist

Do not run Formal Verification tests when there is no output from Yosys to compare.

tests/formal/passlist.txt

@@ -293,8 +293,6 @@ sv2v:core/class_param_nest.v
 sv2v:core/constexpr.v
 sv2v:core/data_lifetime.sv
 sv2v:core/data_lifetime.v
-sv2v:core/edge.sv
-sv2v:core/edge.v
 sv2v:core/empty_args.sv
 sv2v:core/empty_args.v
 sv2v:core/empty_args_hier.sv
@@ -448,9 +446,6 @@ sv2v:error/macro_args_empty.sv
 sv2v:error/macro_arg_bad_name.sv
 sv2v:error/size_cast_neg_lit_1.sv
 sv2v:error/size_cast_neg_lit_2.sv
-sv2v:error/size_cast_xpr_lit.sv
-sv2v:error/size_cast_x_lit.sv
-sv2v:error/size_cast_zero_lit.sv
 sv2v:lex/block_comment.sv
 sv2v:lex/block_comment.v
 sv2v:lex/comment_no_space.sv

tests/formal/skiplist.txt

@@ -66,3 +66,15 @@ sv2v:core/paramtype_param_default.sv
 sv2v:core/paramtype_stagger.sv
 # Yosys mishandles a negative signed constant which is interpreted correctly by the plugin.
 yosys:simple/case_expr_non_const.v
+# Yosys hangs and causes a timeout.
+# There's nothing to compare with the plugin in Formal Verification.
+# Also these tests are non-synthesizable.
+sv2v:error/size_cast_xpr_lit.sv
+sv2v:error/size_cast_x_lit.sv
+sv2v:error/size_cast_zero_lit.sv
+# Yosys aborts in Fmt::parse_verilog due to unsupported format.
+# There's nothing to compare with the plugin in Formal Verification.
+# This test is non-synthesizable.
+sv2v:core/edge.v
+# Yosys fails with syntax error, unexpected TOK_ID. This test is non-synthesizable.
+sv2v:core/edge.sv