xray-core: use `$(INSTALL_DATA)` to install configuration files

Using `$(INSTALL_CONF)` will cause the program has no access to
configurations file when someone enabled the selinux support.

Signed-off-by: Tianling Shen <cnsztl@immortalwrt.org>

net/xray-core/Makefile

@@ -113,7 +113,7 @@ define Package/xray-core/install
 	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/bin/main $(1)/usr/bin/xray
 
 	$(INSTALL_DIR) $(1)/etc/xray/
-	$(INSTALL_CONF) $(CURDIR)/files/config.json.example $(1)/etc/xray/
+	$(INSTALL_DATA) $(CURDIR)/files/config.json.example $(1)/etc/xray/
 
 	$(INSTALL_DIR) $(1)/etc/config/
 	$(INSTALL_CONF) $(CURDIR)/files/xray.conf $(1)/etc/config/xray
@@ -126,8 +126,8 @@ endef
 
 define Package/xray-example/install
 	$(INSTALL_DIR) $(1)/etc/xray/
-	$(INSTALL_CONF) $(CURDIR)/files/vpoint_socks_vmess.json $(1)/etc/xray/
-	$(INSTALL_CONF) $(CURDIR)/files/vpoint_vmess_freedom.json $(1)/etc/xray/
+	$(INSTALL_DATA) $(CURDIR)/files/vpoint_socks_vmess.json $(1)/etc/xray/
+	$(INSTALL_DATA) $(CURDIR)/files/vpoint_vmess_freedom.json $(1)/etc/xray/
 endef
 
 define Package/xray-geodata/install