[chore] Remove unused GH env var from makefile (open-telemetry#9033)

The env var is not being used. `gh` command is used directly in the
shell scripts, not make targets.

Author: dmitryax

.github/workflows/scripts/release-prepare-release.sh

@@ -26,14 +26,14 @@ git add --all
 git commit -m "Changelog update ${RELEASE_VERSION}"
 
 if [ "${CANDIDATE_STABLE}" != "" ]; then
-    make prepare-release GH=none PREVIOUS_VERSION="${CURRENT_STABLE}" RELEASE_CANDIDATE="${CANDIDATE_STABLE}" MODSET=stable
+    make prepare-release PREVIOUS_VERSION="${CURRENT_STABLE}" RELEASE_CANDIDATE="${CANDIDATE_STABLE}" MODSET=stable
     COMMANDS+="
-- make prepare-release GH=none PREVIOUS_VERSION=${CURRENT_STABLE} RELEASE_CANDIDATE=${CANDIDATE_STABLE} MODSET=stable"
+- make prepare-release PREVIOUS_VERSION=${CURRENT_STABLE} RELEASE_CANDIDATE=${CANDIDATE_STABLE} MODSET=stable"
 fi
 if [ "${CANDIDATE_BETA}" != "" ]; then
-    make prepare-release GH=none PREVIOUS_VERSION="${CURRENT_BETA}" RELEASE_CANDIDATE="${CANDIDATE_BETA}" MODSET=beta
+    make prepare-release PREVIOUS_VERSION="${CURRENT_BETA}" RELEASE_CANDIDATE="${CANDIDATE_BETA}" MODSET=beta
     COMMANDS+="
-- make prepare-release GH=none PREVIOUS_VERSION=${CURRENT_BETA} RELEASE_CANDIDATE=${CANDIDATE_BETA} MODSET=beta"
+- make prepare-release PREVIOUS_VERSION=${CURRENT_BETA} RELEASE_CANDIDATE=${CANDIDATE_BETA} MODSET=beta"
 fi
 git push origin "${BRANCH}"
 

Makefile.Common

@@ -33,8 +33,6 @@ MULTIMOD     := $(TOOLS_BIN_DIR)/multimod
 PORTO        := $(TOOLS_BIN_DIR)/porto
 YQ           := $(TOOLS_BIN_DIR)/yq
 
-GH := $(shell which gh)
-
 .PHONY: install-tools
 install-tools: $(TOOLS_BIN_NAMES) $(YQ)