Delete some redundant .gitignore files

build/ToolsetPackages/.gitignore

-# The project.json in this directory exists simply to download packages; since
-# nothing will ever read the project.lock.json here, we should not check them
-# in
-
-project.lock.json

src/EditorFeatures/.gitignore

-# We cannot ignore project.lock.json everywhere in our codebase
-# since we need the files to be checked in for Linux and Mac builds.
-# This tree (src/EditorFeatures) doesn't build at all under those builds
-# so we can delete them here.
-
-project.lock.json

src/ExpressionEvaluator/.gitignore

-# We cannot ignore project.lock.json everywhere in our codebase
-# since we need the files to be checked in for Linux and Mac builds.
-# This tree (src/ExpressionEvaluator) doesn't build at all under those builds
-# so we can delete them here.
-
-project.lock.json

src/Features/.gitignore

-# We cannot ignore project.lock.json everywhere in our codebase
-# since we need the files to be checked in for Linux and Mac builds.
-# This tree (src/Features) doesn't build at all under those builds
-# so we can delete them here.
-
-project.lock.json

src/VisualStudio/.gitignore

-# We cannot ignore project.lock.json everywhere in our codebase
-# since we need the files to be checked in for Linux and Mac builds.
-# This tree (src/VisualStudio) doesn't build at all under those builds
-# so we can delete them here.
-
-project.lock.json