[conda build config] relax build time pins to avoid conflicts

bob/devtools/data/conda_build_config.yaml

@@ -100,32 +100,33 @@ pkg_config:
 # Ideally we want to build against the oldest possible version of packages when
 # we are linking against them. It is best to keep this in sync with:
 # https://github.com/AnacondaRecipes/aggregate/blob/master/conda_build_config.yaml
+# The level of pins (x, x.x, or x.x.x) depends on the run_exports of the package
 boost:
-  - 1.73.0
+  - 1.73
 ffmpeg:
-  - 4.2.2
+  - 4.2
 freetype:
-  - 2.9.1
+  - 2.10
 giflib:
-  - 5.1.4
+  - 5
 hdf5:
   - 1.10.6
 jpeg:
-  - 9b
+  - 9
 libblitz:
   - 1.0.1
 libpng:
-  - 1.6.35
+  - 1.6
 libsvm:
   - 3.24
 libtiff:
-  - 4.1.0
+  - 4.1
 mkl:
-  - 2019.4
+  - 2019
 numpy:
-  - 1.16.6
+  - 1.16
 pybind11:
-  - 2.4.3
+  - 2.4
 sox:
   - 14.4.2
 vlfeat: