Remove code that was needed to support old searx instances

[return42]

After old searx instances has been removed from the list

• https://github.com/searxng/searx-instances/discussions/336
• https://github.com/searxng/searx-space/issues/141
• https://github.com/searxng/searx-space/pull/144

we can do some code cleanups.

Debian

• https://github.com/searxng/searx-space/blob/master/searxstats/data/fetch_deb_hashes.py

https://github.com/searxng/searx-space/blob/f254f0422d0250efd5a042f0e3e65cff289b1c7a/searxstats/config.py#L62-L65

What else?

This is a non-exhaustive list / hints are welcome

[dalf]

• https://github.com/search?q=repo%3Asearxng%2Fsearx-space%20SEARX_GIT_REPOSITORY%20&type=code
• https://github.com/searxng/searx-space/blob/3603b08e70d177a657fa5032fb1ce1d76e4cf1ed/searxstats/config.py#L69
• https://github.com/searxng/searx-space/blob/3603b08e70d177a657fa5032fb1ce1d76e4cf1ed/searxstats/config.py#L71-L72
• Since all SearXNG instances support the simple theme: this part and usage of this part can be removed https://github.com/searxng/searx-space/blob/3603b08e70d177a657fa5032fb1ce1d76e4cf1ed/searxstats/fetcher/timing.py#L71-L76