[clang-tidy] Update documentation of check bugprone-unused-return-value [NFC].

The list of checked functions was incomplete in the description.

Reviewed By: aaron.ballman, steakhal

Differential Revision: https://reviews.llvm.org/D111623

Author: balazske

clang-tools-extra/docs/clang-tidy/checks/bugprone-unused-return-value.rst

@@ -10,9 +10,25 @@ Options
 
 .. option:: CheckedFunctions
 
-   Semicolon-separated list of functions to check. Defaults to
-   ``::std::async;::std::launder;::std::remove;::std::remove_if;::std::unique;::std::unique_ptr::release;::std::basic_string::empty;::std::vector::empty``.
-   This means that the calls to following functions are checked by default:
+   Semicolon-separated list of functions to check. The function is checked if
+   the name and scope matches, with any arguments.
+   By default the following functions are checked:
+   ``std::async, std::launder, std::remove, std::remove_if, std::unique,
+   std::unique_ptr::release, std::basic_string::empty, std::vector::empty,
+   std::back_inserter, std::distance, std::find, std::find_if, std::inserter,
+   std::lower_bound, std::make_pair, std::map::count, std::map::find,
+   std::map::lower_bound, std::multimap::equal_range,
+   std::multimap::upper_bound, std::set::count, std::set::find, std::setfill,
+   std::setprecision, std::setw, std::upper_bound, std::vector::at,
+   bsearch, ferror, feof, isalnum, isalpha, isblank, iscntrl, isdigit, isgraph,
+   islower, isprint, ispunct, isspace, isupper, iswalnum, iswprint, iswspace,
+   isxdigit, memchr, memcmp, strcmp, strcoll, strncmp, strpbrk, strrchr,
+   strspn, strstr, wcscmp, access, bind, connect, difftime, dlsym, fnmatch,
+   getaddrinfo, getopt, htonl, htons, iconv_open, inet_addr, isascii, isatty,
+   mmap, newlocale, openat, pathconf, pthread_equal, pthread_getspecific,
+   pthread_mutex_trylock, readdir, readlink, recvmsg, regexec, scandir,
+   semget, setjmp, shm_open, shmget, sigismember, strcasecmp, strsignal,
+   ttyname``
 
    - ``std::async()``. Not using the return value makes the call synchronous.
    - ``std::launder()``. Not using the return value usually means that the