csharp-mode : Fix typos and remove duplicated declaration

* lisp/progmodes/csharp-mode.el (csharp-vsemi-unknown): Rename
to 'csharp-vsemi-unknown-p'.  The code was calling a function that
does not exist due to this typo.
(c-class-decl-kwds): Remove duplicated declaration for csharp.
(csharp-ts-mode--font-lock-settings): Remove duplicated declaration
of 'escape-sequence'.

lisp/progmodes/csharp-mode.el

@@ -197,12 +197,11 @@
 (c-lang-defconst c-at-vsemi-p-fn
   csharp 'csharp-at-vsemi-p)
 
-(defun csharp-vsemi-status-unknown () t)
+(defun csharp-vsemi-status-unknown-p () t)
 
 (c-lang-defconst c-vsemi-status-unknown-p-fn
   csharp 'csharp-vsemi-status-unknown-p)
 
-
 (c-lang-defconst c-modifier-kwds
   csharp '("abstract" "default" "final" "native" "private" "protected"
            "public" "partial" "internal" "readonly" "static" "event" "transient"
@@ -240,9 +239,6 @@
 (c-lang-defconst c-inexpr-class-kwds
   csharp nil)
 
-(c-lang-defconst c-class-decl-kwds
-  csharp '("class" "struct" "interface"))
-
 (c-lang-defconst c-std-abbrev-keywords
   csharp (append (c-lang-const c-std-abbrev-keywords) '("catch" "finally")))
 
@@ -594,7 +590,6 @@ compilation and evaluation time conflicts."
    "[[:blank:]]+Stack Trace:\n"
    "[[:blank:]]+at [^\n]+ in \\([^\n]+\\):line \\([0-9]+\\)"))
 
-
 (eval-after-load 'compile
   (lambda ()
     (dolist
@@ -1081,11 +1076,6 @@ function is called.  Subsequent calls return the first evaluated value."
                 name: (identifier) @font-lock-function-name-face
                 (lambda_expression)))
 
-             :language 'c-sharp
-             :feature 'escape-sequence
-             :override t
-             '((escape_sequence) @font-lock-escape-face)
-
              :language 'c-sharp
              :feature 'directives
              :override t