fix(csp): apply right csp header when status code is 304

[Zuckjet]

Types of changes

• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

Resolve: #8353

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly. (PR: #)
• I have added tests to cover my changes (if not applicable, please state why)
• All new and existing tests are passing.

[codecov-io]

Codecov Report

Merging #8352 (0fab727) into dev (7278b10) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##              dev    #8352   +/-   ##
=======================================
  Coverage   68.55%   68.55%           
=======================================
  Files          91       91           
  Lines        3876     3876           
  Branches     1056     1056           
=======================================
  Hits         2657     2657           
  Misses        991      991           
  Partials      228      228           

Flag	Coverage Δ
unittests	68.55% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/server/src/middleware/nuxt.js	97.53% <100.00%> (ø)

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[pi0]

LGTM. Thanks