Fix inconsistent type of HookTask.Typ

[donlon]

Webhook type has been changed to string (CHAR(16)) in #13664 and will be synced to the database, but this field in webhook.go has not. This may result in ...rm/session_schema.go:339:Sync2() [W] Table hook_task column typ db type is CHAR(16), struct type is VARCHAR(255) error and failure quries.

[codecov-io]

Codecov Report

Merging #14128 (0f34fb9) into master (e0c753e) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #14128      +/-   ##
==========================================
- Coverage   42.37%   42.36%   -0.02%     
==========================================
  Files         726      726              
  Lines       77839    77839              
==========================================
- Hits        32982    32973       -9     
- Misses      39447    39453       +6     
- Partials     5410     5413       +3     

Impacted Files	Coverage Δ
models/webhook.go	69.06% <ø> (ø)
modules/git/tree_entry_nogogit.go	87.50% <0.00%> (-6.25%)	⬇️
modules/charset/charset.go	68.53% <0.00%> (-4.50%)	⬇️
modules/queue/manager.go	62.13% <0.00%> (-2.96%)	⬇️
modules/process/manager.go	72.50% <0.00%> (-2.50%)	⬇️
services/pull/check.go	48.90% <0.00%> (-0.73%)	⬇️
routers/api/v1/repo/pull.go	24.84% <0.00%> (-0.61%)	⬇️
modules/git/utils.go	80.55% <0.00%> (+2.77%)	⬆️
modules/indexer/stats/db.go	56.00% <0.00%> (+8.00%)	⬆️
modules/git/repo_base_nogogit.go	72.72% <0.00%> (+9.09%)	⬆️
... and 1 more

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[lunny]

We need a migration and also varchar maybe better than my previous change.

[donlon]

We need a migration and also varchar maybe better than my previous change.

@lunny I've seen the changes you made on it. I'll close this pr as it's not useful anymore.