Fix scripts following shellcheck

Author: JohnTitor

ci/semver.sh

@@ -72,5 +72,5 @@ for TARGET in $TARGETS; do
     done
 
     # FIXME: Use upstream once it gets rustup.
-    cargo +${NIGHTLY_DATE} semverfork --api-guidelines --target="${TARGET}"
+    cargo semverfork --api-guidelines --target="${TARGET}"
 done

ci/style.sh

@@ -11,7 +11,8 @@ if rustup component add rustfmt-preview ; then
 fi
 
 if shellcheck --version ; then
-    shellcheck -e SC2103 ci/*.sh
+    # GHA's shellcheck is too old (0.4.6) and cannot handle SC2153 correctly.
+    shellcheck -e SC2103 -e SC2153 ci/*.sh
 else
     echo "shellcheck not found"
     exit 1