Fix compile errors

[umireon]

I got following errors on Flatpak. This PR fixes these errors.

/run/build/obs-ocr/src/tesseract-ocr-utils.cpp: In function ‘void tesseract_thread(void*)’:
/run/build/obs-ocr/src/tesseract-ocr-utils.cpp:363:75: error: conversion from ‘int’ to ‘uint16_t’ {aka ‘short unsigned int’} may change value [-Werror=conversion]
  363 |                                                 uint16_t block_size = tf->binarizationBlockSize;
      |                                                                       ~~~~^~~~~~~~~~~~~~~~~~~~~
/run/build/obs-ocr/src/tesseract-ocr-utils.cpp:409:92: error: conversion from ‘int’ to ‘float’ may change value [-Werror=conversion]
  409 |                                                 (float)tf->rescaleTargetSize / imageForOCR.rows;
      |                                                                                ~~~~~~~~~~~~^~~~
cc1plus: all warnings being treated as errors
ninja: build stopped: subcommand failed.
Error: module obs-ocr: Child process exited with code 1

[royshil]

go!