editorconfig: disable trim_trailing_whitespace due to multi-line bugs

The `trim_trailing_whitespace` config is not working well with
multi-line string literals. I've tried to work around
intellij-rust/intellij-rust#5368 twice and now I want to use the
`insta` crate so I'd need to find another workaround. Let's just
disable the config instead. I wouldn't be surprised if other editors
have similar bugs as IntelliJ.

.editorconfig

@@ -2,7 +2,9 @@ root = true
 
 [*]
 end_of_line = lf
-trim_trailing_whitespace = true
+# Turned off because some editors otherwise remove trailing spaces within
+# multi-line string literals (intellij-rust/intellij-rust#5368).
+trim_trailing_whitespace = false
 
 [*.rs]
 indent_style = space

tests/smoke_test.rs

@@ -24,8 +24,10 @@ fn smoke_test() {
 
     let repo_path = test_env.env_root().join("repo");
     // Check the output of `jj status` right after initializing repo
-    let expected_output =
-        "Parent commit: 000000000000 \nWorking copy : 1d1984a23811 \nThe working copy is clean\n";
+    let expected_output = "Parent commit: 000000000000 
+Working copy : 1d1984a23811 
+The working copy is clean
+";
     test_env
         .jj_cmd(&repo_path, &["status"])
         .assert()
@@ -38,8 +40,9 @@ fn smoke_test() {
     std::fs::write(repo_path.join("file3"), "file3").unwrap();
 
     // The working copy's ID should have changed
-    let expected_output = "Parent commit: 000000000000 \nWorking copy : 5e60c5091e43 \nWorking \
-                           copy changes:
+    let expected_output = "Parent commit: 000000000000 
+Working copy : 5e60c5091e43 
+Working copy changes:
 A file1
 A file2
 A file3
@@ -58,15 +61,17 @@ A file3
         .stdout(expected_output);
 
     // Add a commit description
-    let expected_output = "Working copy now at: 6f13b3e41065 add some files\n";
+    let expected_output = "Working copy now at: 6f13b3e41065 add some files
+";
     test_env
         .jj_cmd(&repo_path, &["describe", "-m", "add some files"])
         .assert()
         .success()
         .stdout(expected_output);
 
     // Close the commit
-    let expected_output = "Working copy now at: 6ff8a22d8ce1 \n";
+    let expected_output = "Working copy now at: 6ff8a22d8ce1 
+";
     test_env
         .jj_cmd(&repo_path, &["close"])
         .assert()