Update github.com/google/btree

vendor/github.com/google/btree/.travis.yml

@@ -1 +0,0 @@
-language: go

vendor/github.com/google/btree/README.md

@@ -1,7 +1,5 @@
 # BTree implementation for Go
 
-![Travis CI Build Status](https://api.travis-ci.org/google/btree.svg?branch=master)
-
 This package provides an in-memory B-Tree implementation for Go, useful as
 an ordered, mutable data structure.
 

vendor/github.com/google/btree/btree.go

@@ -12,6 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//go:build !go1.18
+// +build !go1.18
+
 // Package btree implements in-memory B-Trees of arbitrary degree.
 //
 // btree implements an in-memory B-Tree for use as an ordered data structure.
@@ -476,7 +479,7 @@ func (n *node) growChildAndRemove(i int, item Item, minItems int, typ toRemove)
 		child := n.mutableChild(i)
 		// merge with right child
 		mergeItem := n.items.removeAt(i)
-		mergeChild := n.children.removeAt(i + 1)
+		mergeChild := n.children.removeAt(i + 1).mutableFor(n.cow)
 		child.items = append(child.items, mergeItem)
 		child.items = append(child.items, mergeChild.items...)
 		child.children = append(child.children, mergeChild.children...)