docs(build): update GCC to 13.3.Rel1 version

Updating toolchain to the latest production release version
13.3.Rel1 publicly available on:
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads

We build TF-A 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: If5915fdc14a6c65ce58ac7fccfddd6fe85c0d7c9
diff --git a/docs/getting_started/prerequisites.rst b/docs/getting_started/prerequisites.rst
index 42b1ec4..de2da2f 100644
--- a/docs/getting_started/prerequisites.rst
+++ b/docs/getting_started/prerequisites.rst
@@ -27,7 +27,7 @@
         Program          Min supported version
 ======================== =====================
 Arm Compiler             6.18
-Arm GNU Compiler         13.2
+Arm GNU Compiler         13.3
 Clang/LLVM               11.0.0
 Device Tree Compiler     1.4.7
 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 13.2.Rel1 (gcc 13.2) of the Arm
+Testing has been performed with version 13.3.Rel1 (gcc 13.3) 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.