Update LTP to 6.4

Author: pidefrem

README.md

@@ -4,7 +4,7 @@
 
 ![Test with PyTest](https://github.com/jxmorris12/language_tool_python/workflows/Test%20with%20PyTest/badge.svg)
 
-Current LanguageTool version: **6.2**
+Current LanguageTool version: **6.4**
 
 This is a Python wrapper for [LanguageTool](https://languagetool.org). LanguageTool is open-source grammar tool, also known as the spellchecker for OpenOffice. This library allows you to make to detect grammar errors and spelling mistakes through a Python script or through a command-line interface.
 

language_tool_python/download_lt.py

@@ -31,7 +31,7 @@
 BASE_URL = os.environ.get('LTP_DOWNLOAD_HOST', 'https://www.languagetool.org/download/')
 FILENAME = 'LanguageTool-{version}.zip'
 
-LTP_DOWNLOAD_VERSION = '6.2'
+LTP_DOWNLOAD_VERSION = '6.4'
 
 JAVA_VERSION_REGEX = re.compile(
     r'^(?:java|openjdk) version "(?P<major1>\d+)(|\.(?P<major2>\d+)\.[^"]+)"',