Update hashtable documentation with cloning note (#12454)

* Update hashtable documentation with cloning note

Added note about cloning hashtables with a single key and provided an example using PowerShell.

* Update reference/docs-conceptual/learn/deep-dives/everything-about-hashtable.md

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Editorial changes

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Sean Wheeler <sean.wheeler@microsoft.com>

Author: 3 people

reference/docs-conceptual/learn/deep-dives/everything-about-hashtable.md

@@ -1,7 +1,7 @@
 ---
 description: Hashtables are really important in PowerShell so it's good to have a solid understanding of them.
 ms.custom: contributor-KevinMarquette
-ms.date: 06/25/2023
+ms.date: 10/22/2025
 title: Everything you wanted to know about hashtables
 ---
 # Everything you wanted to know about hashtables
@@ -269,6 +269,16 @@ $environments.Keys.Clone() | ForEach-Object {
 }
 ```
 
+> [!NOTE]
+> You can't clone a hashtable containing a single key. PowerShell throws an error. Instead, you
+> convert the **Keys** property to an array, then iterate over the array.
+
+```powershell
+@($environments.Keys) | ForEach-Object {
+    $environments[$_] = 'SrvDev03'
+}
+```
+
 ## Hashtable as a collection of properties
 
 So far the type of objects we placed in our hashtable were all the same type of object. I used ages