docs: Subsitute the right Mbed OS version

* Replace 6.x to 6.4 (Old version which doesn't support Mbed CLI 2)
* Replace 6.y to 6.5 (Supports Mbed CLI 2 and Mbed CLI 1)

Author: jainvikas8

docs/tools/mbed_cli_2/intro.md

@@ -1,7 +1,7 @@
 # Mbed CLI 2
 
-Starting with version 6.x, Mbed OS is moving to Mbed CLI 2. It uses Ninja as a build system, and CMake to generate the build environment and manage the build process in a compiler-independent manner.
+Starting with version 6.5, Mbed OS is moving to Mbed CLI 2. It uses Ninja as a build system, and CMake to generate the build environment and manage the build process in a compiler-independent manner.
 
 Mbed CLI 2 parses the Mbed OS build configuration and outputs it to a format CMake can read. It also provides a user friendly interface to CMake and Ninja so you can configure, generate and execute builds with a single command.
 
-<span class="notes">**Note:** You'll still need Mbed CLI 1 for older versions of Mbed OS (6.x and older). You can install both tools side by side.</span>
+<span class="notes">**Note:** You'll still need Mbed CLI 1 for older versions of Mbed OS (6.4 and older). You can install both tools side by side.</span>

docs/tools/tools_intro.md

@@ -23,22 +23,22 @@ For more information, please see the [Online Compiler page](../build-tools/mbed-
 
 Mbed OS has two versions of its command line tool:
 
-- For 6.y and newer, use Mbed CLI 1 or Mbed CLI 2.
-- For 6.x and older, use Mbed CLI 1.
+- For 6.5 and newer, use Mbed CLI 1 or Mbed CLI 2.
+- For 6.4 and older, use Mbed CLI 1.
 
 You can have both tools installed side by side, so you can work with multiple versions of Mbed OS.
 
-### Mbed CLI 2 - Mbed OS 6.y and newer
+### Mbed CLI 2 - Mbed OS 6.5 and newer
 
-Starting with version 6.x, Mbed OS is moving to Mbed CLI 2. It uses Ninja as a build system, and CMake to generate the build environment and manage the build process in a compiler-independent manner.
+Starting with version 6.5, Mbed OS is moving to Mbed CLI 2. It uses Ninja as a build system, and CMake to generate the build environment and manage the build process in a compiler-independent manner.
 
 Mbed CLI 2 parses the Mbed OS build configuration and outputs it to a format CMake can read. It also provides a user friendly interface to CMake and Ninja so you can configure, generate and execute builds with a single command.
 
 For more information, see the [Mbed CLI 2 page](../build-tools/mbed-cli-2.html).
 
-<span class="notes">**Note:** You'll still need Mbed CLI 1 for older versions of Mbed OS (6.x and older). You can install both tools side by side.</span>
+<span class="notes">**Note:** You'll still need Mbed CLI 1 for older versions of Mbed OS (6.4 and older). You can install both tools side by side.</span>
 
-### Mbed CLI 1 - Mbed OS 6.x and older
+### Mbed CLI 1 - Mbed OS 6.4 and older
 
 A Python-based tool, specifically for Mbed OS. For more information, see the [Mbed CLI 1 page](../build-tools/mbed-cli-1.html).