Remove completed TODO of extra_tests/fstring.py (RustPython#6095)

Author: moreal

extra_tests/snippets/syntax_fstring.py

@@ -54,12 +54,6 @@
 part_spec = ">+#10x"
 assert f"{16:0{part_spec}}{foo}" == '00000+0x10bar'
 
-# TODO: RUSTPYTHON, delete the next block once `test_fstring.py` can successfully parse
-assert f'{10:#{1}0x}' == '       0xa'
-assert f'{10:{"#"}1{0}{"x"}}' == '       0xa'
-assert f'{-10:-{"#"}1{0}x}' == '      -0xa'
-assert f'{-10:{"-"}#{1}0{"x"}}' == '      -0xa'
-
 spec = "bla"
 assert_raises(ValueError, lambda: f"{16:{spec}}")