First of all, you cannot hide individual context menu options using JSON formatting. You can only customize/hide options from command bar at the top.

You can hide "Share" option from command bar using `` as key like:

```
{
	"key": "share",
 "hide": true
}
```

**Documentation**: [Command bar customization syntax reference](https://learn.microsoft.com/en-us/sharepoint/dev/declarative-customization/view-commandbar-formatting)

<hr>

You can hide complete context menu from **list** view using two methods:

**Method 1 - SharePoint OOTB**:

In SharePoint list, Title column has three different variants:

- Title
- Title (linked to item)
- Title (linked to item with edit menu)

So, you can use plain "Title" column in your list view to hide context menu.

**Method 2 - JSON formatting**:

You can add simple JSON formatting on Title column like below to hide context menu:

```
{
 "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json",
 "elmType": "div",
 "txtContent": "@currentField"
}
```

While using JSON formatting, you will loose all OOTB functionality formatting for Title column including default click which open display/view form of list, you can get it back using JSON formatting on Title column like:

```
{
 "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json",
 "elmType": "div",
 "txtContent": "@currentField",
 "customRowAction": {
 "action": "defaultClick"
 },
 "attributes": {
 "class": "sp-field-underline"
 }
}
```
<hr>

**Update from comments**:

As you are using document library, you have to apply column formatting on **Name** column instead of **Title** column: :

Format option: 

[![enter image description here][1]][1]

Then go to "Advanced mode": 

[![enter image description here][2]][2]

Copy-paste above JSON and click "Save":

[![enter image description here][3]][3]

You can apply additional styling as per your requirements. Check below documentation for more information:

1. [Use Column formatting in SharePoint](https://learn.microsoft.com/en-us/sharepoint/dev/declarative-customization/column-formatting)
2. [JSON formatting-syntax-reference](https://learn.microsoft.com/en-us/sharepoint/dev/declarative-customization/formatting-syntax-reference)


 [1]: https://i.sstatic.net/jjLhb.png
 [2]: https://i.sstatic.net/cWt2r.png
 [3]: https://i.sstatic.net/QX51I.png