Delete unused iOS test scripts after LUCI change (#18712)

This deletes old LUCI build scripts that have been unused since
https://flutter-review.googlesource.com/c/recipes/+/3160

testing/ios/IosUnitTests/build_and_run_tests.sh

-#!/bin/sh
-
-set -e
-
-TESTING_DIR=$(dirname "$0")
-pushd $TESTING_DIR
-
-FLUTTER_ENGINE=ios_debug_sim_unopt
-
-if [ $# -eq 1 ]; then
-  FLUTTER_ENGINE=$1
-fi
-
-cd ../../../..
-
-if [ ! -d "out/$FLUTTER_ENGINE" ]; then
-  echo "You must GN to generate out/$FLUTTER_ENGINE"
-  echo "example: ./flutter/tools/gn --ios --simulator --unoptimized"
-  exit 1
-fi
-
-autoninja -C out/$FLUTTER_ENGINE ios_test_flutter
-popd
-$TESTING_DIR/run_tests.sh $FLUTTER_ENGINE

testing/ios/IosUnitTests/run_tests.sh

-#!/bin/sh
-FLUTTER_ENGINE=ios_debug_sim_unopt
-
-TESTING_DIR=$(dirname "$0")
-pushd $TESTING_DIR
-
-if [ $# -eq 1 ]; then
-  FLUTTER_ENGINE=$1
-fi
-
-../../run_tests.py --variant $FLUTTER_ENGINE --type objc --ios-variant $FLUTTER_ENGINE
-
-popd

testing/scenario_app/run_ios_tests.sh

@@ -33,9 +33,6 @@ if [[ $# -eq 1 ]]; then
   FLUTTER_ENGINE="$1"
 fi
 
-# Delete after LUCI push.
-"$SCRIPT_DIR/compile_ios_jit.sh" "$SRC_DIR/out/host_debug_unopt" "$SRC_DIR/out/$FLUTTER_ENGINE/clang_x64"
-
 cd ios/Scenarios
 set -o pipefail && xcodebuild -sdk iphonesimulator \
   -scheme Scenarios \