consolidate copyright statements at bottom of markdown files and add a newline to the end of the file

Author: heckj

Sources/docc/DocCDocumentation.docc/Reference Syntax/API Reference Syntax/Snippet.md

@@ -22,4 +22,5 @@ Place the `Snippet` directive to embed a code example from the project's snippet
 
 If the snippet had slices annotated within it, an individual slice of the snippet can be referenced with the `slice` option. Without the option defined, the directive embeds the entire snippet.
 
-<!-- Copyright (c) 2022 Apple Inc and the Swift Project authors. All Rights Reserved. -->
+<!-- Copyright (c) 2025 Apple Inc and the Swift Project authors. All Rights Reserved. -->
+

Sources/docc/DocCDocumentation.docc/snippets.md

@@ -140,4 +140,5 @@ DocC parses contiguous comments within your the code of a snippet as markdown to
 DocC will attempt to reference symbols from within these comments just like any other documentation content.
 You can reference symbols from your API, which DocC converts into hyperlinks to that symbol when displaying the content.
 
-<!-- Copyright (c) 2024 Apple Inc and the Swift Project authors. All Rights Reserved. -->
+<!-- Copyright (c) 2025 Apple Inc and the Swift Project authors. All Rights Reserved. -->
+