docs(prerequisites): update mbedtls to v3.6.3

Signed-off-by: Lauren Wehrmeister <lauren.wehrmeister@arm.com>
Change-Id: I62bc0fd6e40a38143ad3118a2e8e8d63c728a675
(cherry picked from commit 247ce406f41e91ad0990ae5ae883b8dc6906c3a4)
diff --git a/docs/getting_started/prerequisites.rst b/docs/getting_started/prerequisites.rst
index 51723ea..eec55d9 100644
--- a/docs/getting_started/prerequisites.rst
+++ b/docs/getting_started/prerequisites.rst
@@ -77,7 +77,7 @@
 The following libraries are required for Trusted Board Boot and Measured Boot
 support:
 
-- mbed TLS == 3.6.2 (tag: ``mbedtls-3.6.2``)
+- mbed TLS == 3.6.3 (tag: ``mbedtls-3.6.3``)
 
 These tools are optional: