Update .gitignore to exclude .akdata/ and *.tmp (#5495)

Remove the temp files accidentally added under `tests/pandas/.akdata` in
#5444, and exclude `.akdata` and `*tmp` in .gitignore to prevent new
temp files from being committed.

Author: eric-vo

.gitignore

@@ -2,8 +2,10 @@ arkouda_server
 arkouda_server_real
 arkouda_server_llvm
 arkouda_server_llvm_real
+.akdata/
 .arkouda/
 *.log
+*.tmp
 *_real
 #*#
 .#*