Use delete[] for memory allocated with new[]

This fixes a build failure in the 'clazy' CI.
6 jobs from sign-pdf-with-digital-signature in 26 minutes and 41 seconds (queued for 1 minute and 34 seconds)
Status Job ID Name Coverage
  Build
passed #57941
build

00:04:47

failed #57946
build_android

00:00:37

passed #57942
build_clang_libcpp

00:05:12

passed #57945
build_clazy

00:04:05

passed #57943
build_gcc_49

00:08:58

failed #57944
build_mingw64_fedora

00:03:00

 
Name Stage Failure
failed
build_android Build
class SignatureHandler;
^
3 errors generated.
../poppler/GlobalParams.cc:1011:7: warning: 'WITH_FONTCONFIGURATION_WIN32' is not defined, evaluates to 0 [-Wundef]
#elif WITH_FONTCONFIGURATION_WIN32
^
1 warning generated.
ninja: build stopped: subcommand failed.
ERROR: Job failed: exit code 1
failed
build_mingw64_fedora Build
    inlined from 'void GlobalParams::setupBaseFonts(char*)' at ../poppler/GlobalParamsWin.cc:402:22:
../poppler/GlobalParamsWin.cc:212:16: warning: 'char* strncat(char*, const char*, size_t)' specified bound 260 equals destination size [-Wstringop-overflow=]
strncat(winFontDir, FONTS_SUBDIR, cbWinFontDirLen);
~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[52/389] Building CXX object CMakeFiles/poppler.dir/poppler/Gfx.cc.obj
[53/389] Building CXX object CMakeFiles/poppler.dir/poppler/GfxState.cc.obj
[54/389] Building CXX object CMakeFiles/poppler.dir/poppler/Annot.cc.obj
ninja: build stopped: subcommand failed.
ERROR: Job failed: exit code 1