chore(README): update progress_icon default value (#260)

README.md

@@ -169,7 +169,7 @@ Available options are shown below:
       done_style = "Constant",    -- Highlight group for completed LSP tasks
       progress_ttl = math.huge,   -- How long a message should persist when in progress
       progress_icon =             -- Icon shown when LSP progress tasks are in progress
-        { pattern = "dots", period = 1 },
+        { "dots" },
       progress_style =            -- Highlight group for in-progress LSP tasks
         "WarningMsg",
       group_style = "Title",      -- Highlight group for group name (LSP server name)