Remove duplicate preset declarations

As noted by suggestions by @benlangmuir the presets are actually
duplicated. Therefore, they can safely be removed and not "merged".

Python 3's
[configparser](https://docs.python.org/3/library/configparser.html) does
not parse in the same way that Python 2's did. Specifically, Python 3's
does not allow duplicate sections (or in Swift parlance presets).

Python 3 does provide a "strict" property that can be sent to the
constructor to return to the behavior of Python 2 (e.g.,  `config =
ConfigParser.SafeConfigParser(substitutions, allow_no_value=True,
strict=False)`). However, this provides it's own set of complications in
that the Python 2 version of the constructor does not.

Therefore, instead of having a conditional in the runtime to detect
which version of Python and build the correct initializer this patch
normalizes the presets configuration file such that there are no more
duplicates. This should work in both Python 2 and 3.

Also worth noting: this patch is insufficient by itself to make the
build scripts work with Python 3. This patch is written with the
"Incremental Development" theory in mind and in preparation for other
patches currently in progress.

Author: RLovelett

utils/build-presets.ini

@@ -52,52 +52,6 @@ installable-package=%(installable_package)s
 # If someone uses this for incremental builds, force reconfiguration.
 reconfigure
 
-
-[preset: buildbot,tools=RA,stdlib=DA]
-mixin-preset=
-    mixin_buildbot_trunk_base
-    mixin_buildbot_install_components
-
-# Build Release without debug info, because it is faster to build.
-release
-assertions
-
-dash-dash
-
-swift-stdlib-build-type=Debug
-swift-stdlib-enable-assertions=true
-
-[preset: buildbot,tools=RA,stdlib=RD]
-mixin-preset=
-    mixin_buildbot_trunk_base
-    mixin_buildbot_install_components
-
-# Build Release without debug info, because it is faster to build.
-release
-assertions
-
-dash-dash
-
-swift-stdlib-build-type=RelWithDebInfo
-swift-stdlib-enable-assertions=false
-
-[preset: buildbot,tools=RA,stdlib=RDA]
-mixin-preset=
-    mixin_buildbot_trunk_base
-    mixin_buildbot_install_components
-
-# Build Release without debug info, because it is faster to build.
-release
-assertions
-
-dash-dash
-
-swift-stdlib-build-type=RelWithDebInfo
-swift-stdlib-enable-assertions=true
-
-# This is a release non-incremental build. Run sil-verify-all.
-sil-verify-all
-
 [preset: buildbot,tools=RA,stdlib=RD,test=no]
 mixin-preset=
     mixin_buildbot_trunk_base