gnu: r-openmx: Update to 2.20.0.

* gnu/packages/cran.scm (r-openmx): Update to 2.20.0.
[native-inputs]: Add r-knitr.

gnu/packages/cran.scm

@@ -23942,14 +23942,14 @@ (define-public r-rpf
 (define-public r-openmx
   (package
     (name "r-openmx")
-    (version "2.19.8")
+    (version "2.20.0")
     (source
      (origin
        (method url-fetch)
        (uri (cran-uri "OpenMx" version))
        (sha256
         (base32
-         "0q37mwxqhgdi05rwdfwfapgazfp541xsvw3yskf21lv11y2yjjyb"))))
+         "1flkm5nsvdnqhjayzajv80lsvjbh21v4zbm7ak09051x0giv3shj"))))
     (properties `((upstream-name . "OpenMx")))
     (build-system r-build-system)
     (propagated-inputs
@@ -23963,7 +23963,7 @@ (define-public r-openmx
            r-rcppparallel
            r-rpf
            r-stanheaders))
-    (native-inputs (list gfortran))
+    (native-inputs (list r-knitr gfortran))
     (home-page "http://openmx.ssri.psu.edu")
     (synopsis "Extended structural equation modelling")
     (description