updated macaron go module declaration

[amanbrar1999]

Simple bug fix, the module declaration was not previously updated to match the updated file hierarchy. Fixes issue #352

[MrAlias]

It looks like this needs to be updated in a few places:

% grep -Rn 'go.opentelemetry.io/contrib/instrumentation/macaron'
instrumentation/gopkg.in/macaron.v1/doc.go:20:package macaron // import "go.opentelemetry.io/contrib/instrumentation/macaron"
instrumentation/gopkg.in/macaron.v1/macaron_test.go:46:		assert.Equal(t, "go.opentelemetry.io/contrib/instrumentation/macaron", mockTracer.Name)
instrumentation/gopkg.in/macaron.v1/go.mod:1:module go.opentelemetry.io/contrib/instrumentation/macaron
instrumentation/gopkg.in/macaron.v1/example/server.go:23:	macarontrace "go.opentelemetry.io/contrib/instrumentation/macaron"
instrumentation/gopkg.in/macaron.v1/config.go:33:// "go.opentelemetry.io/contrib/instrumentation/macaron" from the global
instrumentation/gopkg.in/macaron.v1/macaron.go:30:	tracerName = "go.opentelemetry.io/contrib/instrumentation/macaron"

[amanbrar1999]

@MrAlias updates have been made in all requested places

[MrAlias]

Going to merge with one approval given the "typo fix" nature.