Update native coin symbol reference to use environment variable

Author: yavrsky

docker-compose/services/stats.yml

@@ -53,7 +53,7 @@ services:
       - STATS__CONDITIONAL_START__BLOCKS_RATIO__ENABLED=false
       - STATS__CONDITIONAL_START__INTERNAL_TRANSACTIONS_RATIO__ENABLED=false
       - STATS__BLOCKSCOUT_API_URL=http://proxy
-      - STATS_CHARTS__TEMPLATE_VALUES__NATIVE_COIN_SYMBOL=sFUEL
+      - STATS_CHARTS__TEMPLATE_VALUES__NATIVE_COIN_SYMBOL=${NETWORK_CURRENCY_SYMBOL:-sFUEL}
       - STATS_CHARTS__COUNTERS__AVERAGE_TXN_FEE_24H__ENABLED=false
       - STATS_CHARTS__COUNTERS__TXNS_FEE_24H__ENABLED=false
       - STATS_CHARTS__LINE_CHARTS__AVERAGE_TXN_FEE__ENABLED=false