node refs example link updated

[giripriyadarshan]

Description

The NodeRef example has a link in README which does not exist.
Changed it to the actual path.

Checklist

• [ x] I have reviewed my own code
• I have added tests (Not Applicable)

[github-actions]

Size Comparison

examples	master (KB)	pull request (KB)	diff (KB)	diff (%)
async_clock	100.238	100.238	0	0.000%
boids	173.728	173.728	0	0.000%
communication_child_to_parent	92.739	92.739	0	0.000%
communication_grandchild_with_grandparent	105.761	105.761	0	0.000%
communication_grandparent_to_grandchild	101.016	101.016	0	0.000%
communication_parent_to_child	89.083	89.083	0	0.000%
contexts	105.987	105.987	0	0.000%
counter	86.121	86.121	0	0.000%
counter_functional	86.509	86.509	0	0.000%
dyn_create_destroy_apps	88.930	88.930	0	0.000%
file_upload	99.989	99.989	0	0.000%
function_memory_game	172.354	172.354	0	0.000%
function_router	349.661	349.661	0	0.000%
function_todomvc	161.175	161.175	0	0.000%
futures	229.033	229.033	0	0.000%
game_of_life	110.119	110.119	0	0.000%
immutable	185.424	185.424	0	0.000%
inner_html	79.895	79.895	0	0.000%
js_callback	109.506	109.506	0	0.000%
keyed_list	199.563	199.563	0	0.000%
mount_point	82.785	82.785	0	0.000%
nested_list	113.885	113.885	0	0.000%
node_refs	90.323	90.323	0	0.000%
password_strength	1750.041	1750.041	0	0.000%
portals	93.454	93.454	0	0.000%
router	318.577	318.577	0	0.000%
simple_ssr	140.304	140.304	0	0.000%
ssr_router	386.914	386.914	0	0.000%
suspense	115.701	115.701	0	0.000%
timer	88.552	88.552	0	0.000%
timer_functional	97.911	97.911	0	0.000%
todomvc	141.335	141.335	0	0.000%
two_apps	85.824	85.824	0	0.000%
web_worker_fib	134.748	134.748	0	0.000%
web_worker_prime	184.970	184.970	0	0.000%
webgl	82.500	82.500	0	0.000%

✅ None of the examples has changed their size significantly.