ytt formatting converts multi line strings to single line strings due to trailing spaces

**What steps did you take:**
I am running ytt on a config map with a multi line string and a trailing space after the colon in line 7, e.g.:

```
1 apiVersion: v1
2 kind: ConfigMap
3 metadata:
4 name: my-config.map
5 data:
6 config: |
7 metricsConfig:
8 enabled: true
9 path: /metrics
10 port: 9090
11 ignoreErrors: false
12 secure: false

```

**What happened:**
Ytt unexpectedly converts the multi-line string to a single-line string:

```
apiVersion: v1
kind: ConfigMap
metadata:
name: my-config.map
data:
config: "metricsConfig: \n enabled: true\n path: /metrics\n port: 9090\n ignoreErrors: false\n secure: false\n"
```

**What did you expect:**
The multi-line string should be kept. The trailing white space could be removed.

**Environment:**

- ytt version (use `ytt --version`): 0.44.0
- OS (e.g. from `/etc/os-release`): Ubuntu 20.04.4 LTS

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