Style: Add period before returns doc tag (#8535)

- add period before "</returns>" doc tag
- remove extra space before "</returns>" doc tag
- convert first char after "<returns>" doc tag to upper case

src/System.Management.Automation/engine/ProcessCodeMethods.cs

@@ -38,7 +38,7 @@ namespace Microsoft.PowerShell {
         /// CodeMethod for getting the parent process of a process
         /// </summary>
         /// <param name="obj"></param>
-        /// <returns>the parent process, or null if the parent is no longer running</returns>
+        /// <returns>The parent process, or null if the parent is no longer running.</returns>
         public static object GetParentProcess(PSObject obj)
         {
             var process = PSObject.Base(obj) as Process;
@@ -49,7 +49,7 @@ namespace Microsoft.PowerShell {
         /// Returns the parent id of a process or -1 if it fails
         /// </summary>
         /// <param name="process"></param>
-        /// <returns>the pid of the parent process</returns>
+        /// <returns>The pid of the parent process.</returns>
 #if UNIX
         internal static int GetParentPid(Process process)
         {