Move Defender integration doc links (#1172)

Author: ericglau

docs/modules/ROOT/nav.adoc

@@ -1,9 +1,7 @@
 * xref:index.adoc[Overview]
 * xref:hardhat-upgrades.adoc[Using with Hardhat]
-** xref:defender-deploy.adoc[OpenZeppelin Defender integration]
 ** xref:network-files.adoc[Network Files]
 * xref:foundry-upgrades.adoc[Using with Foundry]
-** xref:foundry-defender.adoc[OpenZeppelin Defender integration]
 * xref:writing-upgradeable.adoc[Writing Upgradeable Contracts]
 * xref:proxies.adoc[Proxy Upgrade Pattern]
 * xref:faq.adoc[Frequently Asked Questions]

docs/modules/ROOT/pages/defender-deploy.adoc

@@ -1,4 +1,4 @@
-= OpenZeppelin Defender integration
+= OpenZeppelin Defender with Hardhat
 
 The Hardhat Upgrades package can use https://docs.openzeppelin.com/defender/[OpenZeppelin Defender] for deployments instead of ethers.js, which allows for features such as gas pricing estimation, resubmissions, and automated bytecode and source code verification.
 

docs/modules/ROOT/pages/hardhat-upgrades.adoc

@@ -160,6 +160,10 @@ describe("Box", function() {
 });
 ----
 
+== Usage with Defender
+
+If you are using OpenZeppelin Defender, see xref:defender-deploy.adoc[OpenZeppelin Defender with Hardhat] for how to use it for deployments.
+
 == API
 
 See xref:api-hardhat-upgrades.adoc[Hardhat Upgrades API] for the full API documentation.