remove unused vars

[ben-schwen]

Follows #7487 and removes the following compile warnings

assign.c: In function ‘assign’:
assign.c:368:26: warning: unused variable ‘tc2’ [-Wunused-variable]
  368 |   const char *c1, *tc1, *tc2;
      |                          ^~~
assign.c:368:20: warning: unused variable ‘tc1’ [-Wunused-variable]
  368 |   const char *c1, *tc1, *tc2;
      |                    ^~~
assign.c:368:15: warning: unused variable ‘c1’ [-Wunused-variable]
  368 |   const char *c1, *tc1, *tc2;
      |               ^~
assign.c:365:56: warning: unused variable ‘a’ [-Wunused-variable]
  365 |   SEXP targetcol, nullint, s, colnam, tmp, key, index, a, assignedNames;
      |                                                        ^
assign.c:365:28: warning: unused variable ‘s’ [-Wunused-variable]
  365 |   SEXP targetcol, nullint, s, colnam, tmp, key, index, a, assignedNames;
      |                            ^
dogroups.c: In function ‘dogroups’:
dogroups.c:80:58: warning: unused variable ‘s’ [-Wunused-variable]
   80 |   SEXP ans=NULL, jval, thiscol, BY, N, I, GRP, iSD, xSD, s, RHS, target, source;
      |                                                          ^

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.02%. Comparing base (9029d79) to head (0c25126).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7578   +/-   ##
=======================================
  Coverage   99.02%   99.02%           
=======================================
  Files          87       87           
  Lines       16758    16758           
=======================================
  Hits        16595    16595           
  Misses        163      163           

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[ben-schwen]

Merging since its non user facing, non changing behavior.

[github-actions]

No obvious timing issues in HEAD=unused_vars

Generated via commit 0c25126

Download link for the artifact containing the test results: ↓ atime-results.zip

Task	Duration
R setup and installing dependencies	5 minutes and 20 seconds
Installing different package versions	11 minutes and 15 seconds
Running and plotting the test cases	3 minutes and 41 seconds