Name the version 2.0.0 rather than a third preview (#883)

The two previews are published and the surface has settled: the last thing that
moved between them, the implicit conversion from a collection to a FiniteSet, is
removed and recorded. Nothing in BREAKING-CHANGES.md is now waiting on a decision.

Version only. AssemblyVersion stays pinned at 2.0.0.0 for the whole of 2.x, so a
signed-assembly consumer needs no binding redirect across 2.x releases, and the
NuGet workflow takes the package version from the release tag either way -- this
is what a local build and the assembly metadata carry.

Measured on this commit, .NET 10: 6253 C# tests pass, 0 fail, 14 skipped.

Author: Rafael-SOWNet

BREAKING-CHANGES.md

@@ -15,7 +15,7 @@ read first.
 
 ---
 
-## 2.0.0 (unreleased) — since 1.4.0
+## 2.0.0 — since 1.4.0
 
 ### At a glance
 
@@ -135,9 +135,9 @@ This was not three separate defects. One conversion made *every* `params Entity[
 the library uncallable with a list, including any added later.
 
 **This one moves between previews.** The conversion is in `2.0.0-preview.1` and
-`2.0.0-preview.2`, both published, and is removed in the release that follows them. It is so
-far the only entry here that changes between two previews rather than between releases: a
-reader coming from 1.3.0 or 1.4.0 can ignore the distinction, one already on a preview cannot.
+`2.0.0-preview.2`, both published, and is gone in `2.0.0`. It is the only entry here that
+changes between two previews rather than between releases: a reader coming from 1.3.0 or
+1.4.0 can ignore the distinction, one already on a preview cannot.
 
 **What breaks.** Assigning a list where an `Entity` is expected:
 

Sources/Package.Build.props

@@ -17,7 +17,7 @@
     release tag, so what ships is named by the tag; this is what a local build and the
     assembly metadata carry.
     -->
-    <Version>2.0.0-preview.2</Version>
+    <Version>2.0.0</Version>
 
     <!--
     Pinned to the major for the whole of 2.x, and deliberately not tracking Version.