fix: fix `PATH` of `flyctl` cli in `fly-docker-image` template (#6772)

* Update main.tf

Upgrade coder provider

* fix path in startup_script

* Revert "Update main.tf"

This reverts commit 5037f87a36.

examples/templates/fly-docker-image/main.tf

@@ -281,7 +281,8 @@ resource "coder_agent" "main" {
     sudo hostname -b "${data.coder_workspace.me.name}-fly"
     # Install the Fly CLI and add it to the PATH
     curl -L https://fly.io/install.sh | sh
-    echo "export PATH=\$PATH:/home/coder/.fly" >> ~/.bashrc
+    echo "export PATH=$PATH:/home/coder/.fly/bin" >> ~/.bashrc
+    source ~/.bashrc
   EOT
 }