doc: term-utils/*: fix some warnings from "mandoc -T lint"

doc: term-utils/*: fix some warnings from "mandoc -T lint"

mandoc: ./term-utils/agetty.8:224:36: WARNING: undefined escape, printing literally: \\
mandoc: ./term-utils/agetty.8:12:2: STYLE: fill mode already enabled, skipping: fi
mandoc: ./term-utils/agetty.8:307:2: WARNING: skipping paragraph macro: PP empty
mandoc: ./term-utils/agetty.8:489:2: STYLE: fill mode already enabled, skipping: fi
mandoc: ./term-utils/agetty.8:503:2: STYLE: fill mode already enabled, skipping: fi

mandoc: ./term-utils/script.1:198:2: WARNING: skipping paragraph macro: PP empty
mandoc: ./term-utils/script.1:244:2: WARNING: empty block: RS
mandoc: ./term-utils/script.1:261:2: WARNING: skipping paragraph macro: PP empty

mandoc: ./term-utils/scriptlive.1:77:2: STYLE: fill mode already disabled, skipping: nf

mandoc: ./term-utils/scriptreplay.1:122:2: STYLE: fill mode already disabled, skipping: nf

###

  Additional change:

1)  Changed '  ' once to ' ' in "agetty.8"

2)  Change in the output from "groff":

'-' changed to '\-' in "agetty.8".

Signed-off-by: Bjarni Ingi Gislason <bjarniig@rhi.hi.is>