Simplify find_food

[nmheim]

Scientific-Programming-in-Julia/docs/src/lecture_02/lab.md

Lines 372 to 377 in c77e2a5

	1. Hint: For the functional programming way of coding this can use `filter` and
	`isa` to filter for a certain type and `StatsBase.sample` to choose a random
	element from a vector. You can get an `Iterator` of values of your dictionary
	via `values` which you might want to `collect` before passing it to `sample`.
	2. Hint: You could also program this with a for-loop that iterates over your
	agents in a random order.

Using filter is both slow and not super straight forward in this case. We could remove hint 1 and expand on hint 2.

[nmheim]

closed in favour of #61