cfn/sam autosuggestion not working

Type: Bug

I am not getting autosuggestion after installing AWSToolkit and yaml plugins.
When I'm typing AWST i expected to get autosuggestion to AWSTemplateformatversion.

Extension version: 1.85.0
VS Code version: Code 1.81.1 (6c3e3dba23e8fadc360aed75ce363ba185c49794, 2023-08-09T22:22:42.175Z)
OS version: Windows_NT x64 10.0.19045
Modes:
Connection to 'ssh-remote+t2.micro' could not be established

System Info

|Item|Value|
|---|---|
|CPUs|Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz (4 x 2195)|
|GPU Status|2d_canvas: enabled
canvas_oop_rasterization: disabled_off
direct_rendering_display_compositor: disabled_off_ok
gpu_compositing: enabled
multiple_raster_threads: enabled_on
opengl: enabled_on
rasterization: unavailable_off
raw_draw: disabled_off_ok
video_decode: enabled
video_encode: unavailable_off
vulkan: disabled_off
webgl: enabled
webgl2: enabled
webgpu: enabled|
|Load (avg)|undefined|
|Memory (System)|7.91GB (3.61GB free)|
|Process Argv|--crash-reporter-id a6887d3e-eee2-4060-b629-eaac6dc90121|
|Screen Reader|no|
|VM|0%|

Connection to 'ssh-remote+t2.micro' could not be established

A/B Experiments

```
vsliv368:30146709
vsreu685:30147344
python383cf:30185419
vspor879:30202332
vspor708:30202333
vspor363:30204092
vslsvsres303:30308271
vserr242cf:30382550
pythontb:30283811
vsjup518:30340749
pythonptprofiler:30281270
vshan820:30294714
vstes263cf:30335440
vscorecescf:30445987
vscod805cf:30301675
binariesv615:30325510
bridge0708:30335490
bridge0723:30353136
vsaa593:30376534
pythonvs932:30410667
vsclangdf:30486550
c4g48928:30535728
dsvsc012cf:30540253
pynewext54:30695312
azure-dev_surveyone:30548225
vscccc:30803845
3biah626:30602489
f6dab269:30613381
showlangstatbar:30737416
a2ce3375:30757347
24365598:30736109
pythonfmttext:30731395
pythoncmv:30756943
fixshowwlkth:30771522
showindicator:30805244
pythongtdpath:30769146
i26e3531:30792625
gsofa:30804715
pythonnosmt12:30797651
pythonidxptcf:30805731
pythonnoceb:30805159
asynctok:30815620
dsvsc013:30795093
dsvsc014:30804076
diffeditorv1:30812748

```

No source file or test is named. Start by reproducing the issue in VS Code 1.81.1 with AWS Toolkit 1.85.0 and the YAML plugin, typing AWST in a CloudFormation or SAM file; investigate the AWS Toolkit and YAML plugin interaction. Done means autosuggestion offers AWSTemplateFormatVersion.

Written by the indexing model from the issue text.