remove --all from cargo test

according to the help the option is deprecated and equivalent to `--workspace`
and we haven't a workspace.
Moreover, and most importantly, the option somehow activates features which
should not be present. for example:
`cargo tree --no-default-features -e no-dev --all | grep serde` has dependencies in the output while without `--all` returns nothing

Author: RCasatta

contrib/test.sh

@@ -20,11 +20,11 @@ fi
 if [ "$DO_FEATURE_MATRIX" = true ]
 then
     # Test without any features first
-    cargo test --all --verbose --no-default-features
+    cargo test --verbose --no-default-features
     # Then test with the default features
-    cargo test --all --verbose
+    cargo test --verbose
     # Then test with the default features
-    cargo test --all --all-features --verbose
+    cargo test --all-features --verbose
 
     # Also build and run each example to catch regressions
     cargo build --examples