Support latest package:vm_service (#328)

Closes https://github.com/dart-lang/coverage/issues/321
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 87b5100..d9435e5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.15.1 - 2021-01-14
+
+* Updated dependency on `vm_service` package from `>=1.0.0 < 5.0.0` to `>=1.0.0 <7.0.0`.
+
 ## 0.15.0 - 2021-01-13
 
 * BREAKING CHANGE: Eliminate the `--package-root` option from
diff --git a/lib/src/collect.dart b/lib/src/collect.dart
index caf2ae7..24cdd8e 100644
--- a/lib/src/collect.dart
+++ b/lib/src/collect.dart
@@ -60,7 +60,9 @@
           log: StdoutLog(), disposeHandler: () => socket.close());
       await service.getVM().timeout(_retryInterval);
     } on TimeoutException {
-      service.dispose();
+      // The signature changed in vm_service version 6.0.0.
+      // ignore: await_only_futures
+      await service.dispose();
       rethrow;
     }
   }, _retryInterval, timeout: timeout);
@@ -75,7 +77,9 @@
     if (resume) {
       await _resumeIsolates(service);
     }
-    service.dispose();
+    // The signature changed in vm_service version 6.0.0.
+    // ignore: await_only_futures
+    await service.dispose();
   }
 }
 
diff --git a/pubspec.yaml b/pubspec.yaml
index 11f7b65..e48c1f2 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: coverage
-version: 0.15.0
+version: 0.15.1
 description: Coverage data manipulation and formatting
 homepage: https://github.com/dart-lang/coverage
 
@@ -13,19 +13,13 @@
   path: '>=0.9.0 <2.0.0'
   source_maps: ^0.10.8
   stack_trace: ^1.3.0
-  vm_service: '>=1.0.0 <6.0.0'
+  vm_service: '>=1.0.0 <7.0.0'
 
 dev_dependencies:
   pedantic: ^1.0.0
   test: ^1.16.0-nullsafety.4
   test_descriptor: ^1.2.0
 
-dependency_overrides:
-  test: 1.16.0-nullsafety.13 
-  test_core: 0.3.12-nullsafety.12
-  test_api: 0.2.19-nullsafety.6 
-
 executables:
   collect_coverage:
   format_coverage:
-