fix(shell/server): do not cancel hole commands
fix(shell/server): do not cancel hole commands

Nonterminating hole commands are caught by the timeout anyway.
Fixes #1729.

leanprover/lean,leodemoura/lean,digama0/lean,leanprover/lean,leanprover-community/lean,digama0/lean,fpvandoorn/lean,leanprover/lean,Kha/lean,leanprover/lean,dselsam/lean,Kha/lean,Kha/lean,leodemoura/lean,dselsam/lean,digama0/lean,leanprover/lean,leanprover-community/lean,fpvandoorn/lean,Kha/lean,dselsam/lean,fpvandoorn/lean,fpvandoorn/lean,avigad/lean,johoelzl/lean,leodemoura/lean,johoelzl/lean,johoelzl/lean,leanprover-community/lean,johoelzl/lean,avigad/lean,leanprover-community/lean,Kha/lean,avigad/lean,johoelzl/lean,digama0/lean,fpvandoorn/lean,avigad/lean,johoelzl/lean,dselsam/lean,dselsam/lean,leodemoura/lean,digama0/lean,dselsam/lean,leodemoura/lean,leanprover/lean,leanprover-community/lean,avigad/lean,fpvandoorn/lean,Kha/lean,avigad/lean,leanprover-community/lean,digama0/lean,leodemoura/lean