dev-release: Update git tag command to avoid tagging jgit submodule

We now include jgit as a submodule, and it gets included in invocations
of `git submodule foreach`. Update the example command for tagging the
plugins to avoid also tagging modules/jgit.

Change-Id: Ia8f070c8e07eb65ee0cdb32fdd6a12a5a03b92dd
diff --git a/Documentation/dev-release.txt b/Documentation/dev-release.txt
index 48bafdf..9e1744c 100644
--- a/Documentation/dev-release.txt
+++ b/Documentation/dev-release.txt
@@ -98,7 +98,7 @@
 Tag the plugins:
 
 ----
-  git submodule foreach git tag -s -m "v$version" "v$version"
+  git submodule foreach '[ "$path" == "modules/jgit" ] || git tag -s -m "v$version" "v$version"'
 ----
 
 [[build-gerrit]]