fibheaps/Makefile: remove some weird character

Summary:
Because it's at the beginning of the line with `SRC_HC_OPTS`, it
causes `make` ignore those options. This commit removes that character
and makes everything work.

Signed-off-by: Michal Terepeta <michal.terepeta@gmail.com>

Test Plan: manually verify that the options are passed to GHC

Reviewers: bgamari, dfeuer

Reviewed By: dfeuer

Subscribers: dfeuer

Differential Revision: https://phabricator.haskell.org/D3344

spectral/fibheaps/Makefile

 TOP = ../..
 include $(TOP)/mk/boilerplate.mk
 
-​SRC_HC_OPTS += -package array
+SRC_HC_OPTS += -package array
 
 FAST_OPTS = 5000
 NORM_OPTS = 5000