[ci] Avoiding syncing git submodules unless needed. NFC (#25730)

Also remove outdated comment regarding apple arm64.

Author: sbc100

.circleci/config.yml

@@ -264,9 +264,6 @@ commands:
           # Must be absolute path or relative path from working_directory
           at: ~/
       - checkout
-      - run:
-          name: submodule update
-          command: git submodule update --init
       - emsdk-env
       - bootstrap
       - pip-install
@@ -387,9 +384,6 @@ commands:
           at: ~/
       - checkout
       - remove-linux-binaries
-      - run:
-          name: submodule update
-          command: git submodule update --init
   run-tests-firefox:
     description: "Runs emscripten tests under firefox"
     parameters:
@@ -877,9 +871,6 @@ jobs:
     executor: linux-python
     steps:
       - checkout
-      - run:
-          name: submodule update
-          command: git submodule update --init
       - pip-install
       - install-emsdk
       - run:
@@ -902,9 +893,6 @@ jobs:
     executor: linux-python
     steps:
       - checkout
-      - run:
-          name: submodule update
-          command: git submodule update --init
       - pip-install
       - install-emsdk
       - run:
@@ -932,9 +920,6 @@ jobs:
       EMTEST_SKIP_V8: "1"
     steps:
       - checkout
-      - run:
-          name: submodule update
-          command: git submodule update --init
       - pip-install
       - install-emsdk
       # `install-node-version` only changes the NODE_JS_TEST (the version of
@@ -1093,9 +1078,6 @@ jobs:
       EMTEST_LACKS_WEBGPU: "1"
     steps:
       - checkout
-      - run:
-          name: submodule update
-          command: git submodule update --init
       - pip-install
       - install-emsdk
       - run-tests-chrome:
@@ -1180,9 +1162,6 @@ jobs:
     executor: focal
     steps:
       - checkout
-      - run:
-          name: submodule update
-          command: git submodule update --init
       - pip-install
       - install-emsdk
       - run-tests-firefox:
@@ -1306,9 +1285,9 @@ jobs:
     steps:
       - setup-macos
       - install-emsdk
+      - pip-install:
+          python: "$EMSDK_PYTHON"
       - freeze-cache
-      # TODO: We can't currently do pip install here since numpy and other packages
-      # are currently missing arm64 macos binaries.
       - run-tests:
           title: "crossplatform tests"
           test_targets: "--crossplatform-only"