ci(dependabot): fix package-ecosystem value

[userzimmermann]

• Fixed "go" --> "gomod".

Closes #4

[github-actions]

Benchmark comparison w/ base branch

goos: linux
goarch: amd64
pkg: github.com/zimmermanncode/go-require
cpu: AMD EPYC 7763 64-Core Processor                
            │ base-bench.txt │          head-bench.txt           │
            │     sec/op     │   sec/op     vs base              │
NilPtr-4         2.187n ± 4%   2.183n ± 0%       ~ (p=0.077 n=7)
NotNilPtr-4      2.491n ± 0%   2.493n ± 2%       ~ (p=0.342 n=7)
geomean          2.334n        2.333n       -0.05%

            │ base-bench.txt │           head-bench.txt           │
            │      B/op      │    B/op     vs base                │
NilPtr-4        0.000 ± 0%     0.000 ± 0%       ~ (p=1.000 n=7) ¹
NotNilPtr-4     0.000 ± 0%     0.000 ± 0%       ~ (p=1.000 n=7) ¹
geomean                    ²               +0.00%               ²
¹ all samples are equal
² summaries must be >0 to compute geomean

            │ base-bench.txt │           head-bench.txt           │
            │   allocs/op    │ allocs/op   vs base                │
NilPtr-4        0.000 ± 0%     0.000 ± 0%       ~ (p=1.000 n=7) ¹
NotNilPtr-4     0.000 ± 0%     0.000 ± 0%       ~ (p=1.000 n=7) ¹
geomean                    ²               +0.00%               ²
¹ all samples are equal
² summaries must be >0 to compute geomean

[zimmermannmobile]

Link #4