[Tizen] Remove unused variable in tizen_metadata_handler.cc

Variable "value" of type std::string was declared but never used.
That's why it was removed. Besides it fixes some other nits.
DEPS.xwalk: Roll ozone-wayland (b002e06 -> a4ca316).

a4ca316 Make vkb work on Tizen emulator
1bc6d86 Do not uninitialize input devices when disconnecting the
        devices.

BUG=TC-1373
BUG=TC-2202
Merge pull request #2737 from rakuco/roll-oz-wl

DEPS.xwalk: Roll ozone-wayland (b002e06 -> a4ca316).
Merge pull request #2736 from piotrowskim/rm_unused_metadata_handler

[Tizen] Remove unused variable in tizen_metadata_handler.cc