fix(lsp): set concealcursor='' in LSP floating windows #36596

Problem:
Users often jump and navigate through LSP windows to yank text.
Concealed markdown can make navigation through hyperlinks and code
blocks more difficult.

Solution:
Change 'concealcursor' from 'n' to '' to preserve clean display
while improving navigation and selection of the LSP response.

Closes #36537

test/functional/plugin/lsp/utils_spec.lua

@@ -367,7 +367,7 @@ describe('vim.lsp.util', function()
     screen:expect([[
                                                            |
       ┌─────────┐{1:                                          }|
-      │{100:^local}{101: }{102:foo}│{1:                                          }|
+      │{101:^```}{4:      }│{1:                                          }|
       └─────────┘{1:                                          }|
       {1:~                                                    }|*9
                                                            |
@@ -401,8 +401,8 @@ describe('vim.lsp.util', function()
     screen:expect([[
                                                            |
       ┌─────────┐{1:                                          }|
-      │{4:foo      }│{1:                                          }|
-      │{100:^local}{101: }{102:bar}│{1:                                          }|
+      │{100:local}{101: }{102:bar}│{1:                                          }|
+      │{101:^```}{4:      }│{1:                                          }|
       └─────────┘{1:                                          }|
       {1:~                                                    }|*8
                                                            |