Knights Travails: Remove explicit instruction on search algorithm and implementation

[mao-sz]

Because

#29827 added explicit instruction to use BFS as a "helpful tip", though this directly conflicts with the assignment step to think through DFS and BFS and decide which to use.

I firmly believe that though it's a tricky project, this is still an extremely important learning opp that shouldn't be spoilt (both deciding between the algos and thinking through implementation - learners have been exposed to BFS and DFS implementations before). I do think the original wording is a little vague though (I've come across plenty who'd over-think "search algorithm" and miss that it essentially refers to DFS/BFS).

Other problems include stating that visited positions need tracking - this is only required for DFS and is only an optimisation for BFS. This IMHO is a big part of understanding DFS and BFS, when someone realises how BFS doesn't actually require it.

Landing #30700 will also help learners a lot in the long run, though I believe this PR should be a good middle ground that doesn't need to be blocked until that lands.

This PR

For both pathways' KT projects:

• Removes section explicitly instructing what to use
• Rephrases assignment step for clarity on search algos and key considerations
• Fixes heading case and unnecessary indentations

Issue

Closes #29783

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