Fix path to Empirical directory

[mmore500]

The Makefile in question is examples/ProjectTemplate/Makefile.

The EMP_DIR path is currently listed as ../../Empirical. If we want users to be able to compile the Hello World example in its current location, the EMP_DIR path should be ../../../Empirical. This is the change my PR makes. If we want the user to be able to compile the Hello World Example when the user copies the examples/ProjectTemplate outside of the Empirical directory (e.g., next to it), then EMP_DIR path should be ../Empirical. Either way, the current EMP_DIR needs to be fixed.

[codecov]

Codecov Report

Merging #211 into master will increase coverage by 0.22%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #211      +/-   ##
==========================================
+ Coverage   65.29%   65.52%   +0.22%     
==========================================
  Files          95       95              
  Lines       13223    13223              
==========================================
+ Hits         8634     8664      +30     
+ Misses       4589     4559      -30

Impacted Files	Coverage Δ
source/hardware/AvidaGP.h	52.13% <0%> (+5.21%)	⬆️
source/hardware/AvidaCPU_InstLib.h	77.45% <0%> (+18.62%)	⬆️

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[mmore500]

No code additions were made, so we should override the codecov fail.

[mercere99]

Just a simple addition of ../ to the Empirical path in the Makefile so that the ProjectTemplate compiles in place.