Update operation convert is broken for splice

[DifferentialOrange]

trafficstars

tarantool> box.info.version
---
- 1.10.15-0-ge14d0b4
...

tarantool> crud.update('customers', 1, {{":", "name", 2, 3, "a"}})
---
- null
- line: 177
  class_name: UpdateError
  err: 'Failed to update: Unknown UPDATE operation'
  file: ./crud/update.lua
  str: 'UpdateError: Failed to update: Unknown UPDATE operation'
...

yet it is actually supported by Tarantool 1.10.15. The reason is that the operation is converted to invalid [[":",3,2]] operation: https://github.com/tarantool/crud/blob/48f801c0257f8c948fc8ffaf8992300f814f5b97/crud/common/utils.lua#L776-L778

[DifferentialOrange]

This one is likely to be closed together with 1.10 support drop

[oleg-jukovec]

We need to remove a skip helper from the go-tarantool tests after the fix: https://github.com/tarantool/go-tarantool/pull/353