fix: add git to Dockerfile build (celestiaorg#1017)

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## Overview
Fixes the following error:
```
 ---> 0119ef2bed23
Step 5/12 : RUN make build
 ---> Running in 8f545cb05d38
make: git: No such file or directory
make: git: No such file or directory
--> Updating go.mod
```
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## Checklist

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- [ ] New and updated code has appropriate documentation
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Dockerfile

@@ -1,7 +1,7 @@
 # stage 1 Generate celestia-appd Binary
 FROM golang:1.18-alpine as builder
 # hadolint ignore=DL3018
-RUN apk update && apk --no-cache add make gcc musl-dev
+RUN apk update && apk --no-cache add make gcc musl-dev git
 COPY . /celestia-app
 WORKDIR /celestia-app
 RUN make build