[mono][docs] Reflect current workflow of building individual runtime tests

Due to optimizing effort of building and running runtime tests #54512, some tests don't generate `*.sh` files by default after build. It is necessary to `export BuildAsStandalone=true` or modify the test's `.csproj` file.

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Contributes to: #90254

Author: matouskozak

docs/workflow/testing/mono/testing.md

@@ -20,8 +20,8 @@ cd src/tests
 ./build.sh mono <release|debug>
 ```
 
-To build an individual test, test directory, or a whole subdirectory tree, use the `-test:`, `-dir:` or `-tree:` options (without the src/tests prefix)
-For example: `./build.sh mono release -test:JIT/opt/InstructionCombining/DivToMul.csproj`
+To build an individual test, test directory, or a whole subdirectory tree, use the `-test:`, `-dir:` or `-tree:` options (without the src/tests prefix).
+For example: `./build.sh mono release -test:JIT/opt/InstructionCombining/DivToMul.csproj`. To generate `*.sh` files for tests that are not designed to be run individualy it is necessary to `export BuildAsStandalone=true` before building the test.
 
 
 Run individual test: