Remove a usage of the quiver package

The quiver package has very little usage in the SDK. Drop the only usage
outside of the nnbd migration tool to clear a path towards removing the
dependency from the SDK entirely.

Change-Id: I54b14d6e887fe6e6b067793e7ee9480793893c27
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/148788
Commit-Queue: Nate Bosch <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>
Auto-Submit: Nate Bosch <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: natebosch

pkg/analysis_server/lib/src/services/completion/dart/language_model.dart

@@ -7,7 +7,6 @@ import 'dart:io';
 import 'dart:typed_data';
 
 import 'package:path/path.dart' as path;
-import 'package:quiver/check.dart';
 import 'package:tflite_native/tflite.dart' as tfl;
 
 /// Interface to TensorFlow-based Dart language model for next-token prediction.
@@ -41,9 +40,10 @@ class LanguageModel {
 
     // Get lookback size from model input tensor shape.
     final tensorShape = interpreter.getInputTensors().single.shape;
-    checkArgument(tensorShape.length == 2 && tensorShape.first == 1,
-        message:
-            'tensor shape $tensorShape does not match the expected [1, X]');
+    if (tensorShape.length != 2 || tensorShape.first != 1) {
+      throw ArgumentError(
+          'tensor shape $tensorShape does not match the expected [1, X]');
+    }
     final lookback = tensorShape.last;
 
     return LanguageModel._(interpreter, word2idx, idx2word, lookback);