Remove .gitignore file

Webhooks plugin is promoted to core gerrit plugins and the standalone
build mode was removed, but the .gitignore file was missed to be
removed.

Change-Id: Id973535668c628a937d3d39888443dc15e39affa

.gitignore

diff --git a/.gitignore b/.gitignore
deleted file mode 100644
index 4f44d20..0000000
--- a/.gitignore
+++ /dev/null
@@ -1,9 +0,0 @@
-/.classpath
-/.project
-/.settings/
-/bazel-bin
-/bazel-out
-/bazel-reviewers
-/bazel-testlogs
-/bazel-webhooks
-/eclipse-out/