docs: Streamline upgrade section and remove outdated SQL Server 2014 reference (#36578)

- Remove outdated paragraph about pre-SQL Server 2014 upgrade behavior
- Shorten section header for clarity
- Address customer feedback (UUF 494961) about grammar and clarity

Author: MikeRayMSFT

docs/relational-databases/performance/query-store-usage-scenarios.md

@@ -110,10 +110,8 @@ Plan after missing index creation (plan_id  = 15, below) now has Index Seek (Non
 
 Based on analysis you would likely keep the index as query performance has been improved.  
 
-## <a name="CEUpgrade"></a> Keep performance stability during the upgrade to newer [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)]  
-Prior to [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)], users were exposed to the risk of performance regression during the upgrade to the latest platform version. The reason for that was the fact that latest version of Query Optimizer became active immediately once new bits are installed.  
-  
-Starting with [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)] all Query Optimizer changes are tied to the latest [database compatibility level](../../relational-databases/databases/view-or-change-the-compatibility-level-of-a-database.md), so plans are not changed right at point of upgrade but rather when a user changes the `COMPATIBILITY_LEVEL` to the latest one. This capability, in combination with Query Store gives you a great level of control over the query performance in the upgrade process. Recommended upgrade workflow is shown in the following picture:  
+## <a name="CEUpgrade"></a> Keep performance stability during upgrade  
+Query Optimizer changes are tied to the latest [database compatibility level](../../relational-databases/databases/view-or-change-the-compatibility-level-of-a-database.md), so plans are not changed right at point of upgrade but rather when a user changes the `COMPATIBILITY_LEVEL` to the latest one. This capability, in combination with Query Store gives you a great level of control over the query performance in the upgrade process. Recommended upgrade workflow is shown in the following picture:  
 
 ![Diagram showing the recommended upgrade workflow.](../../relational-databases/performance/media/query-store-usage-5.png "query-store-usage-5")