Update HELM_PLUGIN_SELF -> HELM_PLUGIN_DIR (#10380)

* Update HELM_PLUGIN_SELF -> HELM_PLUGIN_DIR

Signed-off-by: Tyler Auerbeck <tylerauerbeck@users.noreply.github.com>

* Trigger Build

Signed-off-by: Tyler Auerbeck <tylerauerbeck@users.noreply.github.com>

Co-authored-by: Tyler Auerbeck <tylerauerbeck@users.noreply.github.com>

pkg/plugin/plugin_test.go

@@ -193,7 +193,7 @@ func TestLoadDir(t *testing.T) {
 		Version:     "0.1.0",
 		Usage:       "usage",
 		Description: "description",
-		Command:     "$HELM_PLUGIN_SELF/hello.sh",
+		Command:     "$HELM_PLUGIN_DIR/hello.sh",
 		IgnoreFlags: true,
 		Hooks: map[string]string{
 			Install: "echo installing...",

pkg/plugin/testdata/plugdir/good/hello/plugin.yaml

@@ -3,7 +3,7 @@ version: "0.1.0"
 usage: "usage"
 description: |-
   description
-command: "$HELM_PLUGIN_SELF/hello.sh"
+command: "$HELM_PLUGIN_DIR/hello.sh"
 ignoreFlags: true
 hooks:
   install: "echo installing..."