manuals: replace hyphens with em dashes

Fix some hyphens being improperly used as em dashes.
See https://www.grammarly.com/blog/hyphens-and-dashes/

Using em dashes may also allow Sphinx to hyphenate
and break lines in the best way.

Note that the first character after an em dash not
supposed to be capitalized, unless a specific
rule applies, typically when what follows is a proper noun.

Fix a few misuses of parentheses in following text.

(From yocto-docs rev: 5918f019f63f6e820b1168f4cc001faa1d1cdc6f)

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/faq.rst

@@ -364,7 +364,7 @@ redirect requests through proxy servers.
 
 **Q:** Can I get rid of build output so I can start over?
 
-**A:** Yes - you can easily do this. When you use BitBake to build an
+**A:** Yes --- you can easily do this. When you use BitBake to build an
 image, all the build output goes into the directory created when you run
 the build environment setup script (i.e.
 :ref:`structure-core-script`). By default, this :term:`Build Directory`
@@ -428,7 +428,7 @@ relatively normal and the second is not:
       build/tmp/sysroots/x86_64-linux/usr/bin
 
 Even if the paths look unusual,
-they both are correct - the first for a target and the second for a
+they both are correct --- the first for a target and the second for a
 native recipe. These paths are a consequence of the ``DESTDIR``
 mechanism and while they appear strange, they are correct and in
 practice very effective.