fix(mappings): add a note for overriding mapping

Related issue: AstroNvim/AstroNvim#2353 (comment)

src/content/docs/recipes/mappings.mdx

@@ -9,6 +9,12 @@ Mappings can be customized through [AstroCore](https://github.com/AstroNvim/astr
 
 These tables are a direct conversion to the `vim.keymap.set({mode}, {lhs}, {rhs}, {opts})` Lua API. The first key into the table is the `{mode}`, the second key into the table is the `{lhs}`, and the element there is the `{opts}` table with the `{rhs}` in the first key. Also AstroLSP supports adding a `cond` key which can dictate when the mapping should be attached (this is described in detail in the [AstroLSP plugin configuration documentation](https://github.com/AstroNvim/astrolsp#%EF%B8%8F-configuration)) Here is a simple plugin specification example of setting both core and LSP mappings:
 
+:::note
+
+If you want to override a default mapping, the key needs to exactly match (case sensitive) the existing definition in the table; otherwise, there is a race condition. AstroCore uses capital modifiers.
+
+:::
+
 ```lua title="lua/plugins/mappings.lua"
 return {
   {
@@ -33,7 +39,7 @@ return {
           -- this is useful for naming menus
           ["<Leader>b"] = { name = "Buffers" },
           -- quick save
-          -- ["<C-s>"] = { ":w!<cr>", desc = "Save File" },  -- change description but the same command
+          -- ["<C-S>"] = { ":w!<cr>", desc = "Save File" },  -- change description but the same command
         },
         t = {
           -- setting a mapping to false will disable it