Remove unused whereto library

... and the PCRE(3) packages which are required by whereto.

Also remove note about behavior of old pip. Recent pip can resolve
dependencies properly without requiring from a list with no specific
sort order.

Change-Id: I080098d7fba706929673d0b6c25b0e0c1b8ce3f1
Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>

bindep.txt

@@ -25,5 +25,3 @@ python3-all-dev [platform:dpkg]
 python3 [platform:rpm test]
 python3-devel [platform:rpm test]
 sqlite-devel [platform:rpm test]
-libpcre3-dev [platform:dpkg test]
-pcre-devel [platform:rpm test]

doc/requirements.txt

@@ -1,13 +1,5 @@
-# The order of packages is significant, because pip processes them in the order
-# of appearance. Changing the order has an impact on the overall integration
-# process, which may cause wedges in the gate later.
-# Order matters to the pip dependency resolver, so sorting this file
-# changes how packages are installed.  New dependencies should be
-# added in alphabetical order, however, some dependencies may need to
-# be installed in a specific order.
 openstackdocstheme>=2.2.1 # Apache-2.0
 os-api-ref>=1.4.0 # Apache-2.0
 reno>=3.1.0 # Apache-2.0
 sphinx>=2.0.0,!=2.1.0 # BSD
 sphinxcontrib-svg2pdfconverter>=0.1.0 # BSD
-whereto>=0.3.0 # Apache-2.0