Mark the PT grammar as being deprecated. (#4443)

Author: mike-lischke

sql/mysql/Positive-Technologies/README.md

@@ -1,7 +1,8 @@
 # Positive Technologies MySQL grammar
 
-An ANTLR4 grammar for MySQL based on version 5.6 , 5.7 and 8.0 of 
+An ANTLR4 grammar for MySQL based on version 5.6 , 5.7 and 8.0 of
 [http://dev.mysql.com/doc/refman/5.6/en/](http://dev.mysql.com/doc/refman/5.6/en/).
 [http://dev.mysql.com/doc/refman/5.7/en/](http://dev.mysql.com/doc/refman/5.7/en/).
 [http://dev.mysql.com/doc/refman/8.0/en/](http://dev.mysql.com/doc/refman/8.0/en/).
 
+> **This grammar will be removed around end of June 2025.** Pull requests are still possible and the grammar will be tested and updated until the removal date.

sql/mysql/README.md

@@ -2,5 +2,5 @@
 
 This folder contains MySQL grammars from different authors. See the specific sub folders for more details:
 
-* [Oracle](Oracle) - A complete MySQL grammar including the latest language features of MySQL. This grammar is directly derived from the MySQL Yacc server grammar and is updated twice a year to stay in sync with the MySQL server enhancements. It supports all server versions starting from 8.0 and is driving the parsers in the [MySQL Shell for VS Code](https://marketplace.visualstudio.com/items?itemName=Oracle.mysql-shell-for-vs-code). <br/>A **special feature** of this grammar is that you can switch the MySQL server version used at runtime, to adjust things like code completion and syntax checking for the server you are connected to. 
-* [Positive Technologies](Positive-Technologies) - A grammar created from the official documentation (5.6, 5.7, 8.0)
+* [Oracle](Oracle) - A complete MySQL grammar including the latest language features of MySQL. This grammar is directly derived from the MySQL Yacc server grammar and is updated twice a year to stay in sync with the MySQL server enhancements. It supports all server versions starting from 8.0 and is driving the parsers in the [MySQL Shell for VS Code](https://marketplace.visualstudio.com/items?itemName=Oracle.mysql-shell-for-vs-code). <br/>A **special feature** of this grammar is that you can switch the MySQL server version used at runtime, to adjust things like code completion and syntax checking for the server you are connected to.
+* **DEPRECATED** [Positive Technologies](Positive-Technologies) - A grammar created from the official documentation (5.6, 5.7, 8.0). **This grammar will be removed around end of June 2025.** Pull requests are still possible and the grammar will be tested and updated until the removal date.