TUN-9495: Remove references to cloudflare-go

## Summary
When bumping cloudflared to use go1.24, we no longer need cloudflare-go,
since most of the PQ and FIPS compliant curves are already available in go 1.24.
Therefore, we can remove everything related with installing our go toolchain.

Author: jcsf

.teamcity/install-cloudflare-go.sh

@@ -56,8 +56,6 @@ PACKAGE_DIR    := $(CURDIR)/packaging
 PREFIX         := /usr
 INSTALL_BINDIR := $(PREFIX)/bin/
 INSTALL_MANDIR := $(PREFIX)/share/man/man1/
-CF_GO_PATH     := /tmp/go
-PATH           := $(CF_GO_PATH)/bin:$(PATH)
 
 LOCAL_ARCH ?= $(shell uname -m)
 ifneq ($(GOARCH),)
@@ -183,19 +181,10 @@ fuzz:
 	@go test -fuzz=FuzzNewIdentity -fuzztime=600s ./tracing
 	@go test -fuzz=FuzzNewAccessValidator -fuzztime=600s ./validation
 
-.PHONY: install-go
-install-go:
-	rm -rf ${CF_GO_PATH}
-	./.teamcity/install-cloudflare-go.sh
-
-.PHONY: cleanup-go
-cleanup-go:
-	rm -rf ${CF_GO_PATH}
-
 cloudflared.1: cloudflared_man_template
 	sed -e 's/\$${VERSION}/$(VERSION)/; s/\$${DATE}/$(DATE)/' cloudflared_man_template > cloudflared.1
 
-install: install-go cloudflared cloudflared.1 cleanup-go
+install: cloudflared cloudflared.1
 	mkdir -p $(DESTDIR)$(INSTALL_BINDIR) $(DESTDIR)$(INSTALL_MANDIR)
 	install -m755 cloudflared $(DESTDIR)$(INSTALL_BINDIR)/cloudflared
 	install -m644 cloudflared.1 $(DESTDIR)$(INSTALL_MANDIR)/cloudflared.1

.teamcity/mac/install-cloudflare-go.sh

@@ -31,7 +31,7 @@ Downloads are available as standalone binaries, a Docker image, and Debian, RPM,
 * Binaries, Debian, and RPM packages for Linux [can be found here](https://developers.cloudflare.com/cloudflare-one/connections/connect-apps/install-and-setup/installation#linux)
 * A Docker image of `cloudflared` is [available on DockerHub](https://hub.docker.com/r/cloudflare/cloudflared)
 * You can install on Windows machines with the [steps here](https://developers.cloudflare.com/cloudflare-one/connections/connect-apps/install-and-setup/installation#windows)
-* To build from source, first you need to download the go toolchain by running `./.teamcity/install-cloudflare-go.sh` and follow the output. Then you can run `make cloudflared`
+* To build from source, install the required version of go, mentioned in the [Development](#development) section below. Then you can run `make cloudflared`.
 
 User documentation for Cloudflare Tunnel can be found at https://developers.cloudflare.com/cloudflare-one/connections/connect-apps
 
@@ -62,7 +62,7 @@ For example, as of January 2023 Cloudflare will support cloudflared version 2023
 ### Requirements
 - [GNU Make](https://www.gnu.org/software/make/)
 - [capnp](https://capnproto.org/install.html)
-- [cloudflare go toolchain](https://github.com/cloudflare/go)
+- [go >= 1.24](https://go.dev/doc/install)
 - Optional tools:
   - [capnpc-go](https://pkg.go.dev/zombiezen.com/go/capnproto2/capnpc-go)
   - [goimports](https://pkg.go.dev/golang.org/x/tools/cmd/goimports)