Disable the parser cache

I wasn't able to observe a meaningful performance improvement from it, and it requires some file I/O. Here are the times, in seconds, I observed on my ThinkPad T450s with Python 3.6 and Ubuntu 18.04:

                test 1  test 2
    master       8.96    2.59
    this change  8.88    2.62

Test 1 is the total time from:

$ time dash -c 'git clean -dfx && pip install -e . && pytest --ignore tests/test_bin.py'

Test 2 is pytest's reported total time from a subsequent:

$ pytest --ignore tests/test_bin.py

hy/lex/parser.py

@@ -17,10 +17,7 @@
 from .exceptions import LexException, PrematureEndOfInput
 
 
-pg = ParserGenerator(
-    [rule.name for rule in lexer.rules] + ['$end'],
-    cache_id="hy_parser"
-)
+pg = ParserGenerator([rule.name for rule in lexer.rules] + ['$end'])
 
 mangle_delim = 'X'