[DOCS] Fix Helm3 install guide regarding "helm search" command

For helm v3 the correct syntax for "search" command is
"helm search repo [keyword]"

Change-Id: Ie2c824ce5c0cdd38dd38de3b621e8302685dd743
Issue-ID: OOM-2562
Signed-off-by: Bartek Grzybowski <b.grzybowski@partner.samsung.com>
diff --git a/docs/oom_user_guide_helm3.rst b/docs/oom_user_guide_helm3.rst
index 08e9ec0..2c1eeab 100644
--- a/docs/oom_user_guide_helm3.rst
+++ b/docs/oom_user_guide_helm3.rst
@@ -149,7 +149,7 @@
 The Helm search command reads through all of the repositories configured on the
 system, and looks for matches::
 
-  > helm search -l
+  > helm search repo local
   NAME                    VERSION    DESCRIPTION
   local/appc              2.0.0      Application Controller
   local/clamp             2.0.0      ONAP Clamp