Update Makefile

Co-authored-by: Max Horn <max@quendi.de>

Makefile

@@ -2,7 +2,7 @@
 # This Makefile serves two purposes:
 # 1) If the user types "make" without having run "configure", we suggest running configure.
 # 2) Our build system is written for GNU make, and makes liberal use of its features.
-#    We therefore put it into "GNUmakefile", which is picked up by GNU make, but ignore by
+#    We therefore put it into "GNUmakefile", which is picked up by GNU make, but ignored by
 #    other make versions, such as BSD make.
 #    Thus, if the user has BSD make, it will run this Makefile instead -- and we inform
 #    them that they need to use GNU make to compile GAP.