tests: posix: common: Disable for qemu_leon3

This commit disables the `tests/posix/common` test for the `qemu_leon3`
platform because of the alignment-related failure reported in the
GitHub issue zephyrproject-rtos/zephyr#48992.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>
diff --git a/tests/posix/common/testcase.yaml b/tests/posix/common/testcase.yaml
index ae338ae..97cf8d6 100644
--- a/tests/posix/common/testcase.yaml
+++ b/tests/posix/common/testcase.yaml
@@ -1,5 +1,8 @@
 common:
   arch_exclude: posix
+  # FIXME: qemu_leon3 is excluded because of the alignment-related failure
+  #        reported in the GitHub issue zephyrproject-rtos/zephyr#48992.
+  platform_exclude: qemu_leon3
   tags: posix
   min_ram: 64
   timeout: 600