Don't install CHANGES.rst and README.rst to /usr

Upstream's setup.py configuration installs CHANGES.rst and README.rst into /usr. This is fixed in an unmerged pull request, so we can cherry pick the fix.

• Upstream bug report: https://github.com/ikegami-yukino/jaconv/issues/28
• Upstream pull request (only the first commit is relevant): https://github.com/ikegami-yukino/jaconv/pull/37
• Cherry picked commit: https://github.com/ikegami-yukino/jaconv/pull/37/commits/6a1c0fc05f1eac50d5a47d83e988efa1f9a84cf7

PKGBUILD

@@ -18,6 +18,13 @@ checkdepends=(python-nose
 source=(git+https://github.com/ikegami-yukino/jaconv#tag=v$pkgver)
 sha256sums=('08e0c00dd152bc3e6e0537cc1ed04b669ce7cdf855bbc83cca556b808f951642')
 
+prepare() {
+  cd $_pyname
+  # Don't install {CHANGES,README}.rst to /usr
+  # Upstream bug report: https://github.com/ikegami-yukino/jaconv/issues/28
+  git cherry-pick -n 6a1c0fc05f1eac50d5a47d83e988efa1f9a84cf7
+}
+
 build() {
   cd $_pyname
   python -m build --wheel --no-isolation