Remove stray declarations in grammar

[lam2mo]

These two lines in the grammar define tokens that aren't used anywhere in the grammar and should be removed.

less-java/src/main/antlr/LJ.g4

Line 146 in 31556a8

INCR: '++';

less-java/src/main/antlr/LJ.g4

Line 147 in 31556a8

DECR: '--';

Because these lines are currently not doing anything, I'm going to tag this as a "help wanted" newbie-friendly change that we can leave for someone who has just joined the project and needs something to learn the Git workflow.