Changed memmap dependency

[evanxg852000]

Closes (#1111)

Change dependency from memmap:v0.7 to memmap2:v0.3

[codecov]

Codecov Report

Merging #1120 (e5a87dd) into main (ff48135) will decrease coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1120      +/-   ##
==========================================
- Coverage   89.52%   89.50%   -0.03%     
==========================================
  Files         203      203              
  Lines       20231    20231              
==========================================
- Hits        18112    18107       -5     
- Misses       2119     2124       +5     

Impacted Files	Coverage Δ
src/directory/mmap_directory.rs	87.83% <100.00%> (ø)
src/directory/directory.rs	78.04% <0.00%> (-12.20%)	⬇️

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