teensy: Remove the teensy port.

This port is largely unmaintained, has limited features (the only hardware
support is for GPIO and timer, and no machine module), only supports a
small number of Teensy boards, and can be confused with the mimxrt support
for Teensy 4.x.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
Signed-off-by: Damien George <damien@micropython.org>

.github/workflows/ports_teensy.yml

@@ -1,28 +0,0 @@
-name: teensy port
-
-on:
-  push:
-  pull_request:
-    paths:
-      - '.github/workflows/*.yml'
-      - 'tools/**'
-      - 'py/**'
-      - 'extmod/**'
-      - 'shared/**'
-      - 'lib/**'
-      - 'drivers/**'
-      - 'ports/teensy/**'
-
-concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
-  cancel-in-progress: true
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v4
-    - name: Install packages
-      run: source tools/ci.sh && ci_teensy_setup
-    - name: Build
-      run: source tools/ci.sh && ci_teensy_build