remove useless gems

Gemfile

Gemfile.lock

public/pdfjs/LICENSE

public/pdfjs/build/pdf.js

public/pdfjs/build/pdf.worker.js

public/pdfjs/web/cmaps/78-EUC-H.bcmap

public/pdfjs/web/cmaps/78-EUC-V.bcmap

public/pdfjs/web/cmaps/78-H.bcmap

public/pdfjs/web/cmaps/78-RKSJ-H.bcmap

public/pdfjs/web/cmaps/78-RKSJ-V.bcmap

public/pdfjs/web/cmaps/78-V.bcmap

public/pdfjs/web/cmaps/78ms-RKSJ-H.bcmap

public/pdfjs/web/cmaps/78ms-RKSJ-V.bcmap

public/pdfjs/web/cmaps/83pv-RKSJ-H.bcmap

public/pdfjs/web/cmaps/90ms-RKSJ-H.bcmap

public/pdfjs/web/cmaps/90ms-RKSJ-V.bcmap

public/pdfjs/web/cmaps/90msp-RKSJ-H.bcmap

public/pdfjs/web/cmaps/90msp-RKSJ-V.bcmap

public/pdfjs/web/cmaps/90pv-RKSJ-H.bcmap

public/pdfjs/web/cmaps/90pv-RKSJ-V.bcmap