chore: remove content_topic specific API

[weboko]

Problem

We have experimented with API for subscriptions and noticed it was not used.
Preferred way will be to use #2034

Solution

Remove unused files as per agreement https://discord.com/channels/1110799176264056863/1263257970058461214/1263257972453277746

[github-actions]

size-limit report 📦

Path	Size	Loading time (3g)	Running time (snapdragon)	Total time
Waku node	118.93 KB (-35.33% 🔽)	2.4 s (-35.33% 🔽)	30.3 s (+63.23% 🔺)	32.7 s
Waku Simple Light Node	183.78 KB (-0.18% 🔽)	3.7 s (-0.18% 🔽)	20.7 s (+3.99% 🔺)	24.3 s
ECIES encryption	23.12 KB (0%)	463 ms (0%)	6.4 s (-2.67% 🔽)	6.9 s
Symmetric encryption	22.58 KB (0%)	452 ms (0%)	5.9 s (+22.02% 🔺)	6.4 s
DNS discovery	72.49 KB (0%)	1.5 s (0%)	11 s (-34.17% 🔽)	12.5 s
Peer Exchange discovery	74.22 KB (0%)	1.5 s (0%)	11 s (-22.61% 🔽)	12.5 s
Local Peer Cache Discovery	67.68 KB (0%)	1.4 s (0%)	13.7 s (+15.2% 🔺)	15.1 s
Privacy preserving protocols	38.87 KB (0%)	778 ms (0%)	12.8 s (+20.44% 🔺)	13.6 s
Waku Filter	113.31 KB (0%)	2.3 s (0%)	12.7 s (-13.28% 🔽)	15 s
Waku LightPush	111.31 KB (0%)	2.3 s (0%)	17.8 s (-11.5% 🔽)	20 s
History retrieval protocols	111.81 KB (0%)	2.3 s (0%)	20.5 s (-3.77% 🔽)	22.8 s
Deterministic Message Hashing	7.29 KB (0%)	146 ms (0%)	3 s (+1.61% 🔺)	3.1 s

[danisharora099]

looks good. I'd suggest the PR title to be: chore: remove content_topic specific API