Merge pull request #7982 from hyoshioka0128/patch-17

Typo ".Sln"→".sln"

Author: jborsecnik

docs/extensibility/internals/solution-dot-sln-file.md

@@ -1,5 +1,5 @@
 ---
-title: Solution (.Sln) file
+title: Solution (.sln) file
 description: Learn about the .sln file, which is one of the files that maintains state information for a project in Visual Studio.
 ms.custom: SEO-VS-2020
 ms.date: 03/15/2019