fixing synthesis release notes

[alexanderivrii]

Summary

Just a few days ago @mtreinish has reminded me (yet again) about the difference between an upgrade note and a feature note:

An upgrade note is reserved for something that we want to document might require user input when upgrading from the previous release to the new one. Examples would be a breaking api change, minimum dependency version bump, etc.

and of course we forgot about this in some of the recently merged PRs (probably because we keep copying and adapting the notes from previously merged PRs).

This tiny PRs classifies the release notes correctly. And attention @Cryoris with #12588.

[qiskit-bot]

One or more of the following people are relevant to this code:

• @Qiskit/terra-core

[Cryoris]

Noted 😉

[coveralls]

Pull Request Test Coverage Report for Build 9775510065

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 10 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.01%) to 89.842%

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Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/expr.rs	1	94.02%
crates/qasm2/src/lex.rs	3	93.13%
crates/qasm2/src/parse.rs	6	97.61%

Totals
Change from base Build 9775174998:	0.01%
Covered Lines:	65070
Relevant Lines:	72427

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💛 - Coveralls