Fix reversed NL op codes for floor/ceil

[jsiirola]

Fixes #2213

Summary/Motivation:

This resolves reversed op codes for floor() and ceil() in the AMPL writer. The updated test baseline (small14.pyomo.nl) was verified to be correct (by diffing against small14.ampl.nl, freshly regenerated using AMPL).

Changes proposed in this PR:

• reverse the op codes for floor/ceil in the NL writer
• update a test baseline (the baseline appears to have been testing an erroneous behavior)

Legal Acknowledgement

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1. I agree my contributions are submitted under the BSD license.
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[codecov]

Codecov Report

Merging #2216 (dc86edf) into main (c2e92b9) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #2216   +/-   ##
=======================================
  Coverage   82.97%   82.97%           
=======================================
  Files         607      607           
  Lines       76782    76782           
=======================================
  Hits        63709    63709           
  Misses      13073    13073           

Impacted Files	Coverage Δ
pyomo/repn/plugins/ampl/ampl_.py	87.67% <ø> (ø)

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