[less] The each function has incorrect linting inside a keyframes at-rule

Issue Type: <b>Bug</b> The LESS linter raises false positive errors regarding the `each` function when used inside an `@keyframes` at-rule. Example: ```less @steps: 0%, 50%, 100%; @keyframes foo { each(@steps, { // ^ "{ expected" @{value} { // ^ "} expected" width: @value; } // ^ "at-rule or selector expected" }); } // <- "at-rule or selector expected" ``` There is nothing wrong with the example above - it transpiles into ```css @keyframes foo { 0% { width: 0%; } 50% { width: 50%; } 100% { width: 100%; } } ``` VS Code version: Code 1.64.2 (f80445acd5a3dadef24aa209168452a3d97cc326, 2022-02-09T22:02:28.252Z) OS version: Windows_NT x64 10.0.19044 Restricted Mode: No <details> <summary>System Info</summary> |Item|Value| |---|---| |CPUs|Intel(R) Core(TM) i5-4440 CPU @ 3.10GHz (4 x 3093)| |GPU Status|2d_canvas: enabled<br>gpu_compositing: enabled<br>multiple_raster_threads: enabled_on<br>oop_rasterization: enabled<br>opengl: enabled_on<br>rasterization: enabled<br>skia_renderer: enabled_on<br>video_decode: enabled<br>vulkan: disabled_off<br>webgl: enabled<br>webgl2: enabled| |Load (avg)|undefined| |Memory (System)|7.94GB (2.50GB free)| |Process Argv|C:\\Users\\REDACTED --crash-reporter-id b1616fa4-2d33-455f-9b3a-0973b302cc16| |Screen Reader|no| |VM|0%| </details><details><summary>Extensions (10)</summary> Extension|Author (truncated)|Version ---|---|--- vscode-cylc|cyl|1.0.3 gitlens|eam|12.0.6 git-graph|mhu|1.30.0 easy-less|mrc|1.7.3 python|ms-|2022.4.1 vscode-pylance|ms-|2022.4.3 jupyter|ms-|2022.1.1301854968 jupyter-keymap|ms-|1.0.0 jupyter-renderers|ms-|1.0.6 remote-wsl|ms-|0.64.2 (1 theme extensions excluded) </details><details> <summary>A/B Experiments</summary> ``` vsliv368:30146709 vsreu685:30147344 python383:30185418 vspor879:30202332 vspor708:30202333 vspor363:30204092 pythonvspyl392:30443607 pythontb:30283811 pythonvspyt551:30345470 pythonptprofiler:30281270 vshan820:30294714 vstes263:30335439 vscoreces:304…