Fix error message when saving generated LOCAL_ROOT_URL config

[tiqwab]

What is saved here is LOCAL_ROOT_URL not JWT secret.

[codecov-commenter]

Codecov Report

Merging #15880 (842c902) into main (b6b8b19) will decrease coverage by 0.02%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main   #15880      +/-   ##
==========================================
- Coverage   44.00%   43.98%   -0.03%     
==========================================
  Files         681      681              
  Lines       82270    82270              
==========================================
- Hits        36205    36185      -20     
- Misses      40158    40175      +17     
- Partials     5907     5910       +3     

Impacted Files	Coverage Δ
cmd/web.go	0.00% <0.00%> (ø)
modules/indexer/stats/db.go	42.85% <0.00%> (-7.15%)	⬇️
modules/charset/charset.go	71.71% <0.00%> (-4.05%)	⬇️
services/pull/temp_repo.go	26.59% <0.00%> (-3.20%)	⬇️
services/pull/check.go	26.02% <0.00%> (-2.74%)	⬇️
services/pull/patch.go	54.23% <0.00%> (-1.70%)	⬇️
modules/queue/unique_queue_disk_channel.go	53.73% <0.00%> (-1.50%)	⬇️
models/repo_list.go	77.04% <0.00%> (-0.78%)	⬇️
models/error.go	39.37% <0.00%> (-0.48%)	⬇️
modules/util/timer.go	85.71% <0.00%> (+42.85%)	⬆️

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[zeripath]

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