Remove init_internalization from enkf_main

[oyvindeide]

This sets the internalization flag for all observations to ensure
they are loaded, however it is only ever read for GEN_DATA which
always sets the flag on allocation.

Pre review checklist

• Added appropriate release note label
• PR title captures the intent of the changes, and is fitting for release notes.
• Commit history is consistent and clean, in line with the contribution guidelines.

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[codecov-commenter]

Codecov Report

Merging #3719 (3be2a62) into main (5355501) will increase coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #3719      +/-   ##
==========================================
+ Coverage   63.37%   63.40%   +0.03%     
==========================================
  Files         594      594              
  Lines       46003    45978      -25     
  Branches     4142     4139       -3     
==========================================
- Hits        29153    29151       -2     
+ Misses      15561    15537      -24     
- Partials     1289     1290       +1     

Impacted Files	Coverage Δ
src/libres/lib/enkf/enkf_main.cpp	43.47% <ø> (+2.36%)	⬆️
src/res/enkf/enkf_main.py	95.60% <ø> (-0.02%)	⬇️
src/ert/data/record/_transformation.py	88.57% <0.00%> (-0.48%)	⬇️
src/libres/lib/res_util/block_fs.cpp	67.34% <0.00%> (-0.41%)	⬇️

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[eivindjahren]

LGTM