gnu: r-rcpparmadillo: Update to 0.7.700.0.0.

* gnu/packages/statistics.scm (r-rcpparmadillo): Update to 0.7.700.0.0.
[source]: Do not delete bundled armadillo sources, because upstream no longer
hosts previous versions.
[propagated-inputs]: Remove "armadillo-for-rcpparmadillo".
[arguments]: Remove because we no longer need to link with the armadillo
library.
* gnu/packages/bioinformatics.scm (r-deseq2)[arguments]: Remove because we no
longer need to link with armadillo library.