docs: Fix path to gcc toolchain file

Fix wrong path to gcc toolchain file in the template for README.md that
goes into each generated example.

Signed-off-by: Lingkai Dong <lingkai.dong@arm.com>

templates/common/README.md.in

@@ -27,14 +27,14 @@ To configure CMake to use a particular toolchain you must pass in a
 
 The example will automatically fetch the default toolchain files for
 * Arm Compiler 6: `--toolchain toolchains/toolchain-armclang.cmake`
-* GNU Arm Embedded Toolchain (GCC) `--toolchain toolchains/arm-none-eabi-gcc.cmake`
+* GNU Arm Embedded Toolchain (GCC) `--toolchain toolchains/toolchain-arm-none-eabi-gcc.cmake`
 
 ### Configuration and building
 
 To configure this example, e.g. using GCC:
 
 ```
-cmake -B __build -GNinja --toolchain toolchains/arm-none-eabi-gcc.cmake
+cmake -B __build -GNinja --toolchain toolchains/toolchain-arm-none-eabi-gcc.cmake
 ```
 
 **Notes**: