docs: fix some typos

Signed-off-by: jingchanglu <jingchanglu@outlook.com>

Author: jingchanglu

docs/build/opl/celer/ping-example.md

@@ -182,7 +182,7 @@ ping 0.001 tBNB (1000000 gwei) will be enough.
 :::info
 
 For the `Sapphire Testnet` an executor is running to relay the messages every
-few mintues. If you deploy on mainnet please refer to the [Executor chapter].
+few minutes. If you deploy on mainnet please refer to the [Executor chapter].
 
 :::
 

docs/build/opl/opl-sdk/ping-example.md

@@ -208,7 +208,7 @@ Finally execute the function `startPing`.
 :::info
 
 For the `Sapphire Testnet` an executor is running to relay the messages every
-few mintues. If you deploy on mainnet please refer to the [Executor chapter].
+few minutes. If you deploy on mainnet please refer to the [Executor chapter].
 :::
 
 [Executor chapter]:  ../celer/README.md#executor