Reduce "occasional" tests for now

Author: aitap

.github/workflows/R-CMD-check-occasional.yaml

@@ -16,17 +16,9 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [macOS-latest, windows-latest, ubuntu-latest]
-        r: ['devel', 'release', '3.5', '3.6', '4.0', '4.1', '4.2', '4.3', '4.4', '4.5']
-        locale: ['en_US.utf8',
-                 # Multibyte characters: Mandarin
-                 'zh_CN.utf8',
-                 # Encoding: non-UTF-8 locales for French, Mandarin, and Russian
-                 'fr_CA', 'zh_CN.GB18030', 'ru_RU.KOI8-R', # fr_CA is implicitly 'ISO-8859-1'
-                 # Collate order (#3502, see also #7837): Latvian, Azeri, Hungarian, Faroese, Albanian
-                 'lv_LV.utf8', 'az_AZ.utf8', 'hu_HU.utf8', 'fo_FO.utf8', 'sq_MK.utf8',
-                 # Local time formatting (for R bug #19117)
-                 'vi_VN.utf8']
+        os: [ubuntu-latest]
+        r: ['3.5']
+        locale: [ 'ru_RU.KOI8-R' ]
         # we're constrained by GHA inflexibility to do a tedious thing here with 'exclude' below.
         #   better would be for GHA to support multiple 'matrix' configs (one for ubuntu, one for other OS);
         #   an approach with multiple jobs would tediously require copy-pasting the _rest_ of the steps