Manager: Rephrase wording on report for successfully writing to Shared Storage

* Replace "OK!" with "successfully"
  Remove exclamation mark since there is no need to call for attention.
  Use "successfully" as it is more descriptive in this case than OK,
  which can have other meanings.

internal/manager/api_impl/meta.go

@@ -142,7 +142,7 @@ func (f *Flamenco) CheckSharedStoragePath(e echo.Context) error {
 
 	// There is a directory, and we can create a file there. Should be good to go.
 	return e.JSON(http.StatusOK, api.PathCheckResult{
-		Cause:    "Directory checked OK!",
+		Cause:    "Directory checked successfully",
 		IsUsable: true,
 		Path:     path,
 	})

internal/manager/api_impl/meta_test.go

@@ -91,7 +91,7 @@ func TestCheckSharedStoragePath(t *testing.T) {
 	assertResponseJSON(t, echoCtx, http.StatusOK, api.PathCheckResult{
 		Path:     mf.tempdir,
 		IsUsable: true,
-		Cause:    "Directory checked OK!",
+		Cause:    "Directory checked successfully",
 	})
 	files, err := filepath.Glob(filepath.Join(mf.tempdir, "*"))
 	if assert.NoError(t, err) {