[MINOR] Change DNNLSTM to use MatrixBlockReshape

[Baunsgaard]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 57.14286% with 3 lines in your changes missing coverage. Please review.

Project coverage is 72.40%. Comparing base (5ff6274) to head (ee0536d).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...he/sysds/runtime/matrix/data/LibMatrixDNNLSTM.java	57.14%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2218      +/-   ##
============================================
+ Coverage     72.38%   72.40%   +0.01%     
- Complexity    45381    45391      +10     
============================================
  Files          1468     1468              
  Lines        170802   170802              
  Branches      33306    33306              
============================================
+ Hits         123634   123662      +28     
+ Misses        37762    37747      -15     
+ Partials       9406     9393      -13     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.