Document lower bound of memtx_memory config & fix doc examples

[Korablev77]

Product: Tarantool
Root document: https://www.tarantool.io/en/doc/latest/reference/configuration/#initialization-file
SME: @
Peer reviewer: @

Details

memtx_memory value can't be lower than 32 mb (33554432 bytes). However examples in docs somewhere contain lower value. For example: https://www.tarantool.io/en/doc/latest/reference/configuration/#initialization-file

Related to #2299

[patiencedaur]

https://www.tarantool.io/en/doc/latest/book/cartridge/cartridge_api/modules/cartridge.argparse/#parse
This description contains an invalid value of memtx_memory
However, it looks like nothing changes whether you run this command with a valid or invalid --memtx-memory flag value (33554436 or 100 – no difference). Probably there is a typo?