samples: Bluetooth: central_hr: Fix prj_minimal.conf use

Fix prj_minimal.conf as the project configuration and not as
the extra configuration for the sample.

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>

samples/bluetooth/central_hr/prj_minimal.conf

diff --git a/samples/bluetooth/central_hr/prj_minimal.conf b/samples/bluetooth/central_hr/prj_minimal.conf
index 983b5a9..d5cd3f2 100644
--- a/samples/bluetooth/central_hr/prj_minimal.conf
+++ b/samples/bluetooth/central_hr/prj_minimal.conf
@@ -1,6 +1,7 @@
 CONFIG_BT=y
 CONFIG_BT_SMP=y
 CONFIG_BT_CENTRAL=y
+CONFIG_BT_GATT_CLIENT=y
 
 # Drivers and peripherals
 CONFIG_I2C=n

samples/bluetooth/central_hr/sample.yaml

diff --git a/samples/bluetooth/central_hr/sample.yaml b/samples/bluetooth/central_hr/sample.yaml
index 9dbcf35..81a1b3b 100644
--- a/samples/bluetooth/central_hr/sample.yaml
+++ b/samples/bluetooth/central_hr/sample.yaml
@@ -11,7 +11,7 @@
       - bbc_microbit
     integration_platforms:
       - bbc_microbit
-    extra_args: EXTRA_CONF_FILE=prj_minimal.conf
+    extra_args: CONF_FILE=prj_minimal.conf
     tags: bluetooth
   sample.bluetooth.central_hr.bt_ll_sw_split.extended:
     harness: bluetooth