[docs][llvm-symbolizer] Fix --functions syntax highlighting

[jhenderson]

Summary

The text for the --functions switch in the llvm-symbolizer document had the '[' after the option in bold, like the option name, and unlike the rest of the args string. This was wrong. The only way I could come up with to fix this was to replace the '=' with a space (matching the Sphinx documentation). To make the other options consistent, I've removed the '=' from them too.

docs/CommandGuide/llvm-symbolizer.rst

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 .. option:: -obj, -exe, -e
 
   Path to object file to be symbolized.
 
 .. _llvm-symbolizer-opt-f:
 
-.. option:: -functions[=<none|short|linkage>], -f
+.. option:: -functions [<none|short|linkage>], -f
 
   Specify the way function names are printed (omit function name,
   print short function name, or print full linkage name, respectively).
   Defaults to ``linkage``.
 
 .. _llvm-symbolizer-opt-use-symbol-table:
 
 .. option:: -use-symbol-table

 .. option:: -default-arch
 
  If a binary contains object files for multiple architectures (e.g. it is a
  Mach-O universal binary), symbolize the object file for a given architecture.
  You can also specify architecture by writing ``binary_name:arch_name`` in the
  input (see example above). If architecture is not specified in either way,
  address will not be symbolized. Defaults to empty string.
 
-.. option:: -dsym-hint=<path/to/file.dSYM>
+.. option:: -dsym-hint <path/to/file.dSYM>
 
  (Darwin-only flag). If the debug info for a binary isn't present in the default
  location, look for the debug info at the .dSYM path provided via the
  ``-dsym-hint`` flag. This flag can be used multiple times.
 
 .. option:: -print-address, -addresses, -a
 
  Print address before the source code location. Defaults to false.
 
 .. option:: -pretty-print, -p
 
  Print human readable output. If ``-inlining`` is specified, enclosing scope is
  prefixed by (inlined by). Refer to listed examples.
 
 .. option:: -basenames, -s
 
  Strip directories when printing the file path.
 
-.. option:: -adjust-vma=<offset>
+.. option:: -adjust-vma <offset>
 
  Add the specified offset to object file addresses when performing lookups. This
  can be used to perform lookups as if the object were relocated by the offset.
 
 .. _llvm-symbolizer-opt-output-style:
 
-.. option:: -output-style=<LLVM|GNU>
+.. option:: -output-style <LLVM|GNU>
 
   Specify the preferred output style. Defaults to ``LLVM``. When the output
   style is set to ``GNU``, the tool follows the style of GNU's **addr2line**.
   The differences from the ``LLVM`` style are:
   
   * Does not print column of a source code location.
 
   * Does not add an empty line after the report for an address.