Remove the mention of GCC_ARM, IAR as its not very relevant here.

theotherjimmy · SenRamakri · web-flow · commit dadc7db1371f · 2019-03-13T17:21:47.000-05:00
Co-Authored-By: SenRamakri &lt;senthil.ramakrishnan@arm.com&gt;
diff --git a/docs/tools/tools_intro.md b/docs/tools/tools_intro.md
@@ -59,7 +59,7 @@ In this method, you can create or update your `mbed_app.json` with the following
 {
   "target_overrides": {
       "*": {
-          "target.supported_toolchains": ["ARMC5", "GCC_ARM", "IAR"]
+          "target.supported_toolchains": ["ARMC5"]
       }
   }
 }
@@ -79,4 +79,4 @@ See below for example:
 }
 ```
 
-<span class="note"> **Note:** The above methods to override ARM toolchain version is made available only to enable developers migrating from ARM Compiler 5 to ARM Compiler 6. We encourage developers to make plans to switch to ARM Compiler 6 soon, as we plan to deprecate ARM Compiler 5 support in the future and this migration would ensure that your software is compatible with it. </span>
+<span class="note"> **Note:** The above methods to override ARM toolchain version is made available only to enable developers migrating from ARM Compiler 5 to ARM Compiler 6. We encourage developers to make plans to switch to ARM Compiler 6 soon, as we plan to deprecate ARM Compiler 5 support in the future and this migration would ensure that your software is compatible with it. </span>

Original file line number	Diff line number	Diff line change
@@ -59,7 +59,7 @@ In this method, you can create or update your `mbed_app.json` with the following
`59`	`59`	`{`
`60`	`60`	`"target_overrides": {`
`61`	`61`	`"*": {`
`62`		`- "target.supported_toolchains": ["ARMC5", "GCC_ARM", "IAR"]`
	`62`	`+ "target.supported_toolchains": ["ARMC5"]`
`63`	`63`	`}`
`64`	`64`	`}`
`65`	`65`	`}`
`@@ -79,4 +79,4 @@ See below for example:`
`79`	`79`	`}`
`80`	`80`	```
`81`	`81`
`82`		`-<span class="note"> Note: The above methods to override ARM toolchain version is made available only to enable developers migrating from ARM Compiler 5 to ARM Compiler 6. We encourage developers to make plans to switch to ARM Compiler 6 soon, as we plan to deprecate ARM Compiler 5 support in the future and this migration would ensure that your software is compatible with it. </span>`
	`82`	`+<span class="note"> Note: The above methods to override ARM toolchain version is made available only to enable developers migrating from ARM Compiler 5 to ARM Compiler 6. We encourage developers to make plans to switch to ARM Compiler 6 soon, as we plan to deprecate ARM Compiler 5 support in the future and this migration would ensure that your software is compatible with it. </span>`