Restore modified tags after TZ manipulation

[jim-easterbrook]

This ensures that Xmp date/times that have been set by the user aren't
over written by the TZ restoration efforts. This fixes bug #1998

[codecov]

Codecov Report

Merging #1999 (bcc4f1c) into main (fde8ed0) will not change coverage.
The diff coverage is 100.00%.

❗ Current head bcc4f1c differs from pull request most recent head 2e2dd88. Consider uploading reports for the commit 2e2dd88 to get more accurate results

@@           Coverage Diff           @@
##             main    #1999   +/-   ##
=======================================
  Coverage   61.16%   61.16%           
=======================================
  Files          96       96           
  Lines       19255    19255           
  Branches     9862     9862           
=======================================
  Hits        11777    11777           
  Misses       5135     5135           
  Partials     2343     2343           

Impacted Files	Coverage Δ
src/xmpsidecar.cpp	70.00% <100.00%> (ø)

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