docs(build): update GCC toolchain requirement to 14.2.Rel1

Update documentation to reflect the use of GCC version 14.2.Rel1,
the latest production release available at:
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads

TF-A is built in CI using x86_64 Linux-hosted cross toolchains:
---------------------------------------------------------------
* AArch32 bare-metal target (arm-none-eabi)
* AArch64 bare-metal target (aarch64-none-elf)

Signed-off-by: Jayanth Dodderi Chidanand <jayanthdodderi.chidanand@arm.com>
Change-Id: I4cd2c16fa9daac1ce518d2280169e92562e3766d
diff --git a/docs/getting_started/prerequisites.rst b/docs/getting_started/prerequisites.rst
index a043991..da7a2c3 100644
--- a/docs/getting_started/prerequisites.rst
+++ b/docs/getting_started/prerequisites.rst
@@ -27,7 +27,7 @@
         Program          Min supported version
 ======================== =====================
 Arm Compiler             6.23
-Arm GNU Compiler         13.3
+Arm GNU Compiler         14.2
 Clang/LLVM               18.1.8
 Device Tree Compiler     1.6.1
 GNU make                 3.81
@@ -51,7 +51,7 @@
 AArch64 builds, the respective targets required are ``arm-none-eabi`` and
 ``aarch64-none-elf``.
 
-Testing has been performed with version 13.3.Rel1 (gcc 13.3) of the Arm
+Testing has been performed with version 14.2.Rel1 (GCC 14.2) of the Arm
 GNU compiler, which can be installed from the `Arm Developer website`_.
 
 In addition, a native compiler is required to build supporting tools.