Fix name of projects REST API documentation file

It should match the name in Gerrit core which is 'rest-api-projects'
and not 'rest-api-project'.

Change-Id: Iae97823fd8b50f227ef23fff1451dff9d749eabc
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>
diff --git a/src/main/resources/Documentation/rest-api-project.md b/src/main/resources/Documentation/rest-api-projects.md
similarity index 100%
rename from src/main/resources/Documentation/rest-api-project.md
rename to src/main/resources/Documentation/rest-api-projects.md