chore(linters): Fix findings found by testifylint: compares

[zak-pawel]

Address findings for testifylint: compares - checks usage of github.com/stretchr/testify.

❌   assert.True(t, a == b)
     assert.True(t, a != b)
     assert.True(t, a > b)
     assert.True(t, a >= b)
     assert.True(t, a < b)
     assert.True(t, a <= b)
     // And other variations (with assert.False too)...

✅   assert.Equal(t, a, b)
     assert.NotEqual(t, a, b)
     assert.Greater(t, a, b)
     assert.GreaterOrEqual(t, a, b)
     assert.Less(t, a, b)
     assert.LessOrEqual(t, a, b)

It is only part of the bigger job.
After all type of findings in whole project are handled, we can enable testifylint linter in golangci-lint.

[telegraf-tiger]

Download PR build artifacts for linux_amd64.tar.gz, darwin_amd64.tar.gz, and windows_amd64.zip.
Downloads for additional architectures and packages are available below.

☺️ This pull request doesn't significantly change the Telegraf binary size (less than 1%)

📦 Click here to get additional PR build artifacts

Artifact URLs

DEB	RPM	TAR GZ	ZIP
amd64.deb	aarch64.rpm	darwin_amd64.tar.gz	windows_amd64.zip
arm64.deb	armel.rpm	darwin_arm64.tar.gz	windows_arm64.zip
armel.deb	armv6hl.rpm	freebsd_amd64.tar.gz	windows_i386.zip
armhf.deb	i386.rpm	freebsd_armv7.tar.gz
i386.deb	ppc64le.rpm	freebsd_i386.tar.gz
mips.deb	riscv64.rpm	linux_amd64.tar.gz
mipsel.deb	s390x.rpm	linux_arm64.tar.gz
ppc64el.deb	x86_64.rpm	linux_armel.tar.gz
riscv64.deb		linux_armhf.tar.gz
s390x.deb		linux_i386.tar.gz
		linux_mips.tar.gz
		linux_mipsel.tar.gz
		linux_ppc64le.tar.gz
		linux_riscv64.tar.gz
		linux_s390x.tar.gz

[powersj]

Thank you!