Improve C++ standard wording in generated NEWS.md via notes2news.pl

[coderabbitai]

Description

The current C++ standard section in NEWS.md (auto-generated by tools/release-scripts/notes2news.pl) has wordy phrasing that could be tightened for better clarity.

Current wording:

* C++ standard is std17

  * Using this standard, all supported toolchains across our CI matrix will work.
  * The code is not yet modified to use std17:

    * If needed: ``-DCMAKE_CXX_STANDARD=14`` to lower the standard.

Suggested improvement:

* C++ standard: C++17.
  * All supported CI toolchains are covered.
  * To temporarily lower the standard use: ``-DCMAKE_CXX_STANDARD=14``.

Benefits:

• More concise and direct
• Proper C++ version notation (C++17 instead of std17)
• Clearer purpose of the downgrade flag
• Eliminates repetitive phrasing

Context:

Since NEWS.md is auto-generated, this improvement should be made to the notes2news.pl script or its source files.

Backlinks:

• PR: Creation of pgrouting version 4.0.0-alpha1 #2970
• Comment: Creation of pgrouting version 4.0.0-alpha1 #2970 (comment)

Requested by: @cvvergara