docs: use ..note:: to denote non-public build cache

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@huawei.com>

docs/ci/machines-and-flavours.rst

@@ -64,8 +64,9 @@ the Linux flavour of All Scenarios OS and ``MACHINE=seco-intel-b68``. This job
 checks that All Scenarios OS software can be built for the SECO B68 development
 board, which contains an Intel x86_64 SoC.
 
-The cache for this job is not public, pending legal review of any firmware that
-may be included.
+.. note::
+    The cache for this job is not public, pending legal review of any firmware
+    that may be included.
 
 linux-seco-imx8mm-c61
 .....................
@@ -77,8 +78,9 @@ checks that All Scenarios OS software can be built for the SECO C61 development
 board, which contains the NXP i.MX 8M Mini SoC, which implements 64bit ARMv8
 architecture.
 
-The cache for this job is not public, as it contains proprietary elements that
-cannot be redistributed without an agreement with Freescale.
+.. note::
+    The cache for this job is not public, as it contains proprietary elements
+    that cannot be redistributed without an agreement with Freescale.
 
 linux-stm32mp1-av96
 ...................
@@ -90,8 +92,9 @@ that All Scenarios OS software can be built for the 96Boards Avenger development
 board, which contains the STM32MP157 SoC, which implements 32bit ARMv7
 architecture.
 
-The cache for this job is not public, pending legal review of any firmware that
-may be included.
+.. note::
+    The cache for this job is not public, pending legal review of any firmware
+    that may be included.
 
 linux-raspberrypi4-64
 .....................
@@ -103,8 +106,9 @@ checks that All Scenarios OS software can be built for the Raspberry Pi 4B
 development board, which contains the BCM2711 SoC, which implements 64bit ARMv8
 architecture.
 
-The cache for this job is not public, pending legal review of any firmware that
-may be included.
+.. note::
+    The cache for this job is not public, pending legal review of any firmware
+    that may be included.
 
 zephyr-qemu-x86
 ...............
@@ -134,8 +138,9 @@ This job extends `.build-zephyr` job from the manifest repository and builds
 ``MACHINE=96b-nitrogen``. This job checks that Zephyr can be built for the
 96Boards Nitrogen development board, which contains an nRF52832 SoC.
 
-The cache for this job is not public, pending legal review of any firmware that
-may be included.
+.. note::
+    The cache for this job is not public, pending legal review of any firmware
+    that may be included.
 
 zephyr-96b-avenger
 ..................
@@ -146,8 +151,9 @@ This job extends `.build-zephyr` job from the manifest repository and builds
 96Boards Avenger development board cortex-M3 core, embedded into STM32MP157
 SoC.
 
-The cache for this job is not public, pending legal review of any firmware that
-may be included.
+.. note::
+    The cache for this job is not public, pending legal review of any firmware
+    that may be included.
 
 freertos-armv5
 ..............