Remove unused functions in c-ts-mode

Remove unused functions in c-ts-mode

Remove functions that became unused due to the previous change.

* lisp/progmodes/c-ts-mode.el:
(c-ts-mode--standalone-grandparent):
(c-ts-mode--else-heuristic):
(c-ts-mode--first-sibling):
(c-ts-mode--parent-is-not-top-compound):
(c-ts-mode--indent-styles):
(c-ts-mode--top-level-label-matcher): Remove functions.
(c-ts-mode--simple-indent-rules): Move two label rules into
c-ts-mode--label-indent-rules.
(c-ts-mode--label-indent-rules): Add rules

(cherry picked from commit 994258f55675baa8473e6cff9aab7ecb31338580)