Small fixes for signedness warnings in translation service

[zoltanvb]

Description

Current code throws some warnings during compilation:

tasks/task_translation.c: In function ‘parse_response_json’:
tasks/task_translation.c:603:24: warning: comparison of integer expressions of different signedness: ‘int’ and ‘long unsigned int’ [-Wsign-compare]
  603 |          for (i = 0; i < ARRAY_SIZE(ACCESS_RESPONSE_KEYS) && key == -1; i++)
      |                        ^
tasks/task_translation.c: In function ‘translation_response_input’:
tasks/task_translation.c:1100:22: warning: comparison of integer expressions of different signedness: ‘int’ and ‘long unsigned int’ [-Wsign-compare]
 1100 |             for (; i < ARRAY_SIZE(ACCESS_INPUT_LABELS) && !found; i++)
      |                      ^
tasks/task_translation.c: In function ‘translation_dupe_fail’:
tasks/task_translation.c:1318:46: warning: comparison of integer expressions of different signedness: ‘unsigned int’ and ‘int’ [-Wsign-compare]
 1318 |    bool size_equal            = (frame->size == access_st->last_image_size);
      |                                              ^~

Kind of trivial, except for the change in accessibility.h . Negative value for a size could indicate some error situation, but I found no usage for this in the code.

Reviewers

@xunkar @cpod12