Remove --encoded-package-metadata from docs

It's not clear whether or not the option would be added to the GNU linker,
so I"ll make this a hidden option for now.

#1308

docs/mold.md

@@ -629,19 +629,6 @@ but as `-o magic`.
   shared libraries linked with `--pack-dyn-relocs=relr`. As of 2022, only
   ChromeOS, Android and Fuchsia support it.
 
-* `--package-metadata`=_string_, `--encoded-package-metadata`=_string_:
-  Embed _string_ to a `.note.package` section. This option is intended to be
-  used by a package management command such as rpm(8) to embed metadata
-  regarding a package to each executable file.
-
-  The difference between `--package-metadata` and `--encoded-package-metadata`
-  is that the former takes a plain string while the latter takes a
-  percent-encoded string. In other words, `--package-metadata={"foo":"bar"}`
-  is equivalent to `--encoded-package-metadata=%7B%22foo%22%3A%22bar%22%7D`.
-  The latter option is useful to use with the compiler's `-Wl,` option because
-  you can escape commas in a JSON string, which would otherwise be interpreted
-  as an argument separator by the compiler.
-
 * `--pie`, `--pic-executable`, `--no-pie`, `--no-pic-executable`:
   Create a position-independent executable.
 

elf/cmdline.cc

@@ -123,8 +123,6 @@ inline const char helpmsg[] = R"(
   --oformat=binary            Omit ELF, section, and program headers
   --pack-dyn-relocs=[relr,none]
                               Pack dynamic relocations
-  --encoded-package-metadata=PERCENT_ENCODED_STRING
-                              Set a given string to .note.package
   --package-metadata=STRING   Set a given string to .note.package
   --perf                      Print performance statistics
   --pie, --pic-executable     Create a position-independent executable