Remove DEBUG env var from Connect macOS dronegen

It was added in effort to debug flaky Connect builds (#15836).

However, we discovered that the v11.1.0 macOS version of Connect stopped
working. This was likely due to upgrade of electron-builder which recently
updated its process of building native deps
(electron-userland/electron-builder#7196).

In the Node.js ecosystem, the DEBUG env var is typically used to control
which packages emit debug messages [1]. However, after the update of
electron-builder, the env var also changed the behavior of one of the
packages responsible for building the apps.

This was confirmed by inspecting file tree between different app bundles
and running the build locally with DEBUG set to electron-*.

[1] https://www.npmjs.com/package/debug

.drone.yml

@@ -593,7 +593,6 @@ steps:
   - security unlock-keychain -p $${BUILDBOX_PASSWORD} login.keychain
   - security find-identity -v
   - export CSC_NAME=0FFD3E3413AB4C599C53FBB1D8CA690915E33D83
-  - export DEBUG="electron-*"
   - export CONNECT_TSH_BIN_PATH=$WORKSPACE_DIR/go/src/github.com/gravitational/teleport/build/tsh
   - cd $WORKSPACE_DIR/go/src/github.com/gravitational/webapps
   - yarn install && yarn build-term && yarn package-term -c.extraMetadata.version=$VERSION
@@ -8043,7 +8042,6 @@ steps:
   - security unlock-keychain -p $${BUILDBOX_PASSWORD} login.keychain
   - security find-identity -v
   - export CSC_NAME=0FFD3E3413AB4C599C53FBB1D8CA690915E33D83
-  - export DEBUG="electron-*"
   - cd $WORKSPACE_DIR/go/src/github.com/gravitational
   - pkgutil --expand-full tsh-$${VERSION}.pkg tsh
   - export CONNECT_TSH_APP_PATH=$WORKSPACE_DIR/go/src/github.com/gravitational/tsh/Payload/tsh.app
@@ -18269,6 +18267,6 @@ volumes:
   temp: {}
 ---
 kind: signature
-hmac: c50cecb03e9ca4c1a58759cd017fb8555b386f1f45938ae84b56bbb396b36ad3
+hmac: 88e09acfb6869d0ff016262f4beb5fbf66b791abcf6513565f6d3ca1eebb09c3
 
 ...

dronegen/mac.go

@@ -557,8 +557,6 @@ func darwinBuildCommands(toolchainConfig toolchainConfig, artifactConfig darwinA
 			// available.
 			// https://www.electron.build/code-signing
 			`export CSC_NAME=0FFD3E3413AB4C599C53FBB1D8CA690915E33D83`,
-
-			`export DEBUG="electron-*"`,
 		)
 
 		if artifactConfig == binariesWithConnect {