doc: precise trusted storage description

[ktaborowski]

Minor fixes after review

CI parameters

Github_actions:
  #(branch, hash, pull/XXX/head)
  NRF_revision: main

  # Do not change after creating PR
  Create_NRF_PR: false
Jenkins:
  test-sdk-sidewalk: master

Description

JIRA ticket:

Self review

• There is no commented code.
• There are no TODO/FIXME comments without associated issue ticket.
• Commits are properly organized.
• Change has been tested.
• Tests were updated (if applicable).

[github-actions]

Sample		diff	used	total

Memory usage did not change for any of the samples.