fix: There is no main.js (AztecProtocol#3691)

For some reason there was a default export to main.js for aztec.js.
This caused an issue for someone externally, I'm not sure why it only
triggered since last release, where the root exports were explicitly
moved into a "." block.
Regardless, it seems the appropriate thing is just always export
`./dest/index.js`.

yarn-project/aztec.js/package.json

@@ -4,11 +4,7 @@
   "version": "0.1.0",
   "type": "module",
   "exports": {
-    ".": {
-      "node": "./dest/index.js",
-      "import": "./dest/index.js",
-      "default": "./dest/main.js"
-    },
+    ".": "./dest/index.js",
     "./interfaces/pxe": "./dest/api/interfaces/pxe.js",
     "./abi": "./dest/api/abi.js",
     "./aztec_address": "./dest/api/aztec_address.js",