Revert "add MANIFEST.generated to .gitignore"

This reverts commit 5f89700.
Not generated with parrot 5.0, since parrot/parrot#922

Author: Reini Urban

.gitignore

@@ -21,7 +21,6 @@ Makefile
 *.bundle
 *~
 *.pbc
-/MANIFEST.generated
 src/ops/*.h
 src/ops/*.c
 src/pmc/pmc_*.h