sample: uart passthrough: fix filtering and twister file

sample.yml is wrong and was not scanned. Also fix filters in the file so
it can build.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

samples/drivers/uart/passthrough/sample.yaml

@@ -0,0 +1,10 @@
+sample:
+  name: UART Passthrough
+tests:
+  sample.drivers.uart.passthrough:
+    platform_allow:
+      - nucleo_l476rg
+    tags:
+      - serial
+      - uart
+    harness: keyboard

samples/drivers/uart/passthrough/sample.yml

@@ -1,14 +0,0 @@
-sample:
-  name: UART Passthrough
-tests:
-  sample.drivers.uart:
-    integration_platforms:
-      - qemu_x86
-    tags:
-      - serial
-      - uart
-    filter: CONFIG_SERIAL and
-            CONFIG_UART_INTERRUPT_DRIVEN and
-            dt_chosen_enabled("zephyr,console") and
-            dt_chosen_enabled("uart,passthrough")
-    harness: keyboard