Revert "templates: Add {{#let}} block helper."

This reverts commit f81cc16a0f (#17999).

The {{#tr}} helper now includes the functionality that we wanted from
this.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

frontend_tests/node_tests/templates.js

@@ -28,21 +28,6 @@ run_test("or", () => {
     assert.equal(html, "\n<p>last or</p>\n<p>true or</p>\n");
 });
 
-run_test("let", () => {
-    const html = require("./templates/let.hbs")({
-        outer_var: "hello",
-    });
-    assert.equal(
-        html,
-        `\
-    outer_var = hello
-    keyword_var = &lt;b&gt;escaped&lt;/b&gt;
-    block_var =     <b>unescaped</b> with hello
-
-`,
-    );
-});
-
 run_test("rendered_markdown", () => {
     const html = require("./templates/rendered_markdown.hbs")();
     const expected_html =

frontend_tests/node_tests/templates/let.hbs

@@ -1,8 +0,0 @@
-{{#let keyword_var="<b>escaped</b>"}}
-    {{#*inline "block_var"}}
-    <b>unescaped</b> with {{outer_var}}
-    {{/inline}}
-    outer_var = {{outer_var}}
-    keyword_var = {{keyword_var}}
-    block_var = {{block_var}}
-{{/let}}

static/js/templates.js

@@ -48,26 +48,6 @@ Handlebars.registerHelper({
     not(a) {
         return !a || Handlebars.Utils.isEmpty(a);
     },
-    ["let"](options) {
-        // Defines locally scoped variables.
-        // Example usage:
-        //     {{#let name1="value1"}}
-        //         {{#*inline "name2"}}
-        //         value2
-        //         {{/inline}}
-        //         Now {{name1}} and {{name2}} are in scope.
-        //     {{/let}}
-        return options.fn({
-            ...this,
-            ...options.hash,
-            ...Object.fromEntries(
-                Object.entries(options.fn.partials ?? {}).map(([name, value]) => [
-                    name,
-                    new Handlebars.SafeString(value(this)),
-                ]),
-            ),
-        });
-    },
 });
 
 // Note that this i18n caching strategy does not allow us to support

webpack.config.ts

@@ -148,7 +148,6 @@ export default (_env: unknown, argv: {mode?: string}): webpack.Configuration[] =
                                     "and",
                                     "or",
                                     "not",
-                                    "let",
                                     "t",
                                     "tr",
                                     "rendered_markdown",