Fixed typo in Makefile.manual

Changed stdlib_bitsest_64.fypp to stdlib_bitsets_64.fypp in Makefile.manual.

[ticket: X]

Author: wclodius2

src/Makefile.manual

@@ -1,7 +1,7 @@
 SRC = f18estop.f90 \
       stdlib_ascii.f90 \
       stdlib_bitsets.f90 \
-      stdlib_bitsest_64.f90 \
+      stdlib_bitsets_64.f90 \
       stdlib_bitsets_large.f90 \
       stdlib_error.f90 \
       stdlib_io.f90 \