fix typos in citation and benchmark docs (#4604)

Author: zchrissirhcz

CITATION.cff

@@ -7,7 +7,7 @@ type: software
 authors:
   - family-names: "Ni"
     given-names: "Hui"
-  - name: "The ncnn contirbutors"
+  - name: "The ncnn contributors"
 abstract: >-
   ncnn is a high-performance neural network inference
   computing framework optimized for mobile platforms. 

docs/benchmark/the-benchmark-of-caffe-android-lib,-mini-caffe,-and-ncnn.md

@@ -88,7 +88,7 @@ squeezenet
 ![](https://github.com/nihui/ncnn-assets/raw/master/20180413/8.jpg)
 ***
 
-mobilnet
+mobilenet
 
 ![](https://github.com/nihui/ncnn-assets/raw/master/20180413/9.jpg)