Delete the grammar file

It was almost always wrong anyways.

grammar.txt

@@ -1,34 +0,0 @@
-Justfile grammar is a little weird. Because of the freeform
-nature of recipe bodies, we don't tokenize them with the
-same rules as the rest of the justfile. Instead the
-tokenizer will emit a INDENT at the beginning of a recipe
-body, one or more LINEs, which match everything after the
-INDENT whitespace, and a DEDENT at the end.
-
-Thus the lexer is context sensitive, which is a little
-gross.
-
-tokens:
-
-NAME    = /[a-z]((_|-)?[a-z0-9])*/
-EOL     = /\n|\r\n/
-COMMENT = /#[^!].*/
-COLON   = /:/
-INDENT  = emitted when indentation increases
-DEDENT  = emitted when indentation decreases
-LINE    = /.*/ only emitted between INDENT/DEDENT pairs, doesn't include INDENT whitespace
-EOF     = emitted at the end of input
-
-grammar:
-
-justfile = item* EOF
-
-item = COMMENT
-     | recipe
-     | EOL
-
-assignment = NAME EQUALS expression COMMENT? EOL
-
-expression = STRING
-
-recipe = NAME+ COLON NAME* EOL (INDENT LINE+ DEDENT)?