fix: broken link to call a contract page

src/pages/understand-stacks/sending-tokens.md

@@ -60,10 +60,7 @@ const {
   getNonce,
   privateKeyToString,
 } = require('@stacks/transactions');
-const {
+const { StacksTestnet, StacksMainnet } = require('@stacks/network');
-    StacksTestnet,
-    StacksMainnet,
-} = require ('@stacks/network');
 const { TransactionsApi, Configuration } = require('@stacks/blockchain-api-client');
 
 const apiConfig = new Configuration({

src/pages/write-smart-contracts/counter-tutorial.md

@@ -262,3 +262,4 @@ the strengths of performing local development without having to wait for block t
 [clarity language reference]: /references/language-functions
 [transactions]: https://explorer.stacks.co/transactions?chain=testnet
 [clarity visual studio code plugin]: https://marketplace.visualstudio.com/items?itemName=HiroSystems.clarity-lsp
+[call a contract]: https://explorer.stacks.co/sandbox/contract-call?chain=testnet