Fix capitalization in tools_intro.md

Fix capitalization, as requested in comment.

Author: Amanda Butler

docs/tools/tools_intro.md

@@ -21,8 +21,8 @@ We created the Mbed command-line tool (Mbed CLI), a Python-based tool, specifica
 
 Mbed OS 5 can be built with various toolchains. The currently supported versions are:
 
-- [Arm compiler 6.11 (default ARM toolchain)](https://developer.arm.com/products/software-development-tools/compilers/arm-compiler/downloads/version-6).
-- [Arm compiler 5.06 update 6 (to be deprecated in the future)](https://developer.arm.com/products/software-development-tools/compilers/arm-compiler-5/downloads).
+- [Arm Compiler 6.11 (default ARM toolchain)](https://developer.arm.com/products/software-development-tools/compilers/arm-compiler/downloads/version-6).
+- [Arm Compiler 5.06 update 6 (to be deprecated in the future)](https://developer.arm.com/products/software-development-tools/compilers/arm-compiler-5/downloads).
 - [GNU Arm Embedded version  6 (6-2017-q1-update)](https://developer.arm.com/open-source/gnu-toolchain/gnu-rm/downloads).
 - [IAR Embedded Workbench 8.32.1](https://www.iar.com/iar-embedded-workbench/tools-for-arm/arm-cortex-m-edition/).