docs(behavior_path_planner): fix start and goal planner links #28907

Job	Run time
clang-tidy-differential	4m 48s
prevent-no-label-execution / prevent-no-label-execution	1s
build-and-test-differential (humble)	1h 47m 15s
build-and-test-differential (humble, -cuda)	1h 45m 22s
	3h 37m 26s

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