cmd/utils, core: only full sync for fast nodes

[weiihann]

Description

This PR enforces a rule such that when tries-verify-mode is not local, it will always default to full sync instead of snap sync.

Rationale

Snap sync is not supported on fast nodes.

Example

INFO [03-13|13:52:26.157] Starting Geth on BSC mainnet...
INFO [03-13|13:52:26.157] Bumping default cache on mainnet         provided=1024 updated=4096
INFO [03-13|13:52:26.159] Maximum peer count                       ETH=50 total=50
WARN [03-13|13:52:26.163] Only local TriesVerifyMode can support snap sync, resetting to full sync mode=none
...

Changes

• Fixed minor typo