fix(lsp): "bold" border for vim.lsp.buf.hover #33395

Problem: vim.lsp.buf.hover allows a bold border size which hasn't been
defined

Solution: Define the bold border size for vim.lsp.buf.hover
(cherry picked from commit f068386c9f)

runtime/lua/vim/lsp/util.lua

@@ -24,6 +24,7 @@ local border_size = {
   rounded = { 2, 2 },
   solid = { 2, 2 },
   shadow = { 1, 1 },
+  bold = { 2, 2 },
 }
 
 --- Check the border given by opts or the default border for the additional