python-mysqlclient: drop package

The main user for this package was Seafile.
In the meantime, Seafile switch to PyMySQL.
    https://pypi.org/project/PyMySQL/

PyMySQL seems to be a replacement for python-mysqlclient, and while it may
not be fully compatible with the MySQL API, it may be that those APIs
wouldn't be used.

This change drops this package.
If there is enough usage/reason to bring it back, we can.

For python-mysqlclient, the tag-line/description is:
```
This is a fork of MySQLdb1.

This project adds Python 3 support and bug fixes. I hope this fork is
merged back to MySQLdb1 like distribute was merged back to setuptools.
```

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

lang/python/python-mysqlclient/Makefile

@@ -1,41 +0,0 @@
-#
-# Copyright (C) 2007-2018 OpenWrt.org
-#
-# This is free software, licensed under the GNU General Public License v2.
-# See /LICENSE for more information.
-#
-
-include $(TOPDIR)/rules.mk
-
-PKG_NAME:=python-mysqlclient
-PKG_VERSION:=1.4.6
-PKG_RELEASE:=2
-PKG_LICENSE:=GPL-2.0
-
-PYPI_NAME:=mysqlclient
-PKG_HASH:=f3fdaa9a38752a3b214a6fe79d7cae3653731a53e577821f9187e67cbecb2e16
-PKG_MAINTAINER:=Alexandru Ardelean <ardeleanalex@gmail.com>
-
-include ../pypi.mk
-include $(INCLUDE_DIR)/package.mk
-include ../python3-package.mk
-# python-mysqlclient needs iconv
-include $(INCLUDE_DIR)/nls.mk
-
-define Package/python3-mysqlclient
-  SUBMENU:=Python
-  SECTION:=lang
-  CATEGORY:=Languages
-  TITLE:=MySQL database adapter
-  URL:=https://mysqlclient.readthedocs.io/
-  DEPENDS:=+python3 +libmysqlclient
-endef
-
-define Package/python3-mysqlclient/description
- MySQLdb is an thread-compatible interface to the popular MySQL database
- server that provides the Python database API.
-endef
-
-$(eval $(call Py3Package,python3-mysqlclient))
-$(eval $(call BuildPackage,python3-mysqlclient))
-$(eval $(call BuildPackage,python3-mysqlclient-src))