[FLASK] Fix an issue with updating snaps that have caveat permissions

[FrederikBolding]

Explanation

Fixes an issue with updating snaps that had caveat permissions.

Manual Testing Steps

1. Install a previous version of the BIP44 test snap
2. Try to update the snap to the latest version
3. See that this fails on the current build of Flask but not this branch.

[metamaskbot]

Builds ready [0ed4c6f]

• builds: chrome, firefox
• builds (beta): chrome, firefox
• builds (flask): chrome, firefox
• build viz: Build System
• mv3: Background Module Init Stats
• mv3: UI Init Stats
• mv3: Module Load Stats
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• code coverage: Report
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
  • content-script: 0
  • contentscript: contentscript
  • disable-console: disable-console
  • inpage: inpage
  • policy-load: policy-load
  • sentry-install: sentry-install
  • ui: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9

Page Load Metrics (2097 ± 90 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	87	2141	203	445	213
		domContentLoaded	1679	2371	2077	188	90
		load	1680	2371	2097	188	90
		domInteractive	1679	2371	2077	188	90

Bundle size diffs

• background: 0 bytes
• ui: 0 bytes
• common: 0 bytes