fix: remove 'Alpha' prefix from package name (#707)

Author: olavloite

spanner-ado-net/spanner-ado-net/spanner-ado-net.csproj

@@ -6,7 +6,7 @@
     <Nullable>enable</Nullable>
     <LangVersion>default</LangVersion>
     <AssemblyName>Google.Cloud.Spanner.DataProvider</AssemblyName>
-    <PackageId>Alpha.Google.Cloud.Spanner.DataProvider</PackageId>
+    <PackageId>Google.Cloud.Spanner.DataProvider</PackageId>
     <Title>.NET Data Provider for Spanner</Title>
     <Authors>Google</Authors>
     <Version>1.0.0-alpha.20260123102444</Version>